The biggies to me are better screen visibility, swimming HRM, mapping, and more FirstBeat features. I have been using the mapping a lot during corona (running in new places), so that has been a game changer. I love my 945.

935 has this swimming hrm...no?

no

I've had both.

Get the 945 if you can afford it.

First beat metrics
Blood oxygen
Swim HR
Music (if that's your thing)

945 if it's in your budget, otherwise look at the 735 unless you need long battery life. I had the 735 and never really felt compelled to look at upgrading to the 935, but did get the 945 shortly after it came out. Music, maps, and better on watch functionality for a lot of the widgets/metrics felt like a real upgrade. I don't use them all the time, but I use them enough that it still feels like a good upgrade.

For a triathlon, even Iron distance, the 935 is more watch than you will ever need.

But certainly the 945 is better than the 935:
* mapping
* battery life (one aspect that hasn't been mentioned elsewhere in this thread)
* music
* bigger screen allowing additional datafields
* additional firstbeat metrics
* Garmin Pay

If you are into trail/ultrarunning, then the first two may be compelling. Otherwise $200 is a fair bit extra to pay for features that are "nice to have" rather than essential. The question of whether nicer is worth $200 is one that only you can answer.

The battery life on the 945 isn't better than the 935

Not my experience. The battery life is better on the 945.

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Trust me I’m a doctor!
Well, I have a PhD :-)

Mine's worse

From Garmin's specs:

935 with GPS: 24 hours
945 with GPS (no music): 36 hours
945 with GPS and music: 10 hours

I know I am old school, but personally I do like to do my research before posting. Others prefer anecdotes.

You can quote specs all day long, my first one was absolutely horrible. My second one is almost as good as my 935.

935-945

If you set up the 945 with same functions as a 935, the 945 battery will definitely last much longer. If you run a lot of the new features, particularly the pulse Ox meter and music, the 945 battery will last much shorter :-)

The HR is much more stable and accurate on the 945

With current firmware, GPS seems a slightly better on the 945

The 945 screen is easier to read

The 945 optical HR works in the water. On the 935 you have to use the swim or Tri HR strap, good luck keeping that on in a pool swim.

I do not think the 945 has “smart buttons”, which allow short cuts to certain functions with the 935, I miss that capability.

You can get very good used 935s for $ 225-250 (I have one if you PM me), so the price difference is more like
$ 300 :-)

I've also had both, currently using the 945 and do prefer this one however I was lucky with an employer discount ... (also read a couple times that in US there are some healthcare providers(?) that have steep discounts (don't know exactly as I'm in the Netherlands)

main upgrades/features compared to 935 (starting with most significant):
- body battery + stress-status measurement (this really seems to give a good representation of recovery status or upcoming illness! (esp. combined with RHR tracking)
- 6 data fields
- maps
- music
- nfc
- virtual run profile (for zwift running as I don't have a footpod)

nice to haves:
- swim HR (still not sure it is accurate however def. shows "something/trend")
- some more metrics
- sligthly better screen

not so sure:
- GPS accuracy, not better than 935...probably equal in current firmware, still think current run-pace is not always accurate; therefore have lap-pace (auto 1km) on as well (advantage of 6 datafields) ... lap-pace seems spot-on
- GPS-tracking/storage issue in multisport-mode, appeared as if GPS was only saved in +/- 10sec interval instead of 1 sec. (might have been solved??)
- buttons seem to feel differently, less "click"; however they never fail to work so not really an issue I guess
- pulse ox. (never used, apparently not accurate, drains battery)

Hmm

Lots to think about on this.

Thanks all!

Update. I did get the 945 and have been wearing it for the last week. What a huge upgrade from the Vivoactive 3. It's a little big but that's just because I have small wrists. I'll live.

Thanks for the recommendation.

Way too late for the OP, but just one factor for the 945 over the 935 is the broken altimeter/cracking optic HR cover. I've still got my 935 and not wanting to upgrade for features (although the payments would be handy). However unlike the 910xt that I replaced with the 935 after 7 years use (and still going strong), then I know this one will crap out in 2 years (and that's as it's already been replaced under warranty).

If you check then it's a widespread issue - some suggest it's to do with wearing in a warm pool/bath/spa, some related to sunscreen. Personally I am not convinced as I take mine off for spas, otherwise keep on and so don't put sunblock under the watch. And yet my first one still went within 2 years. General internet opinion is the replacements are just the same, ie fixed but break in same way after 18months.

So on that basis, and assuming that they sorted the altimeter on the 945 then I'd think this would be a better investment.

Research is good, but real-life usage for sports gear is always better, from actual regular users.

My 945 was only charged to 55% this morning when I took in on an outdoor 2 hr ride. GPS, bluetooth on, and as well, I left the battery-sucking backlight on continuously for the workout, which they never do in their battery tests.

It drained down to 16% by the time I got home. That's the kind of usage that the online spec searches will never reveal.

Mind you I'm not complaining about the 945 battery life - I'd say it's actually very good for what it does, and I have no complaints. But with my style of usage (backlight always on during workouts) I'm charging it every 2-3 days at least.

is there any indication that the 945 has resolved the barometer issue?
these suggest otherwise
https://forums.garmin.com/...eter-pressure-sensor
https://www.reddit.com/...vation_is_all_wrong/

Oh dear.

I haven't tested it on the 945, but on the 935 I certainly did do some real world experimentation, and found that each 10% of backlight burned about 1.5% of battery per hour. Or about 15% of battery per hour at full brightness. Which is broadly in line with your experience in a 2 hour ride (when you add in GPS usage as well).

But backlight intensity and battery usage IS adjustable. I find 10% works for most purposes (full brightness is way too glary for me, and destroys my night vision). My club does a couple of all-night rides a year (2 hours is just a warmup), and I have finished with plenty of watch battery to spare (although my ageing eyes now prefer me to use an Edge).

Using gesture and timeout will significantly reduce backlight battery usage for most activities, although if mounting the watch on bike handlebars while cycling, just leaving backlight on permanently is probably better.

the music function that allows you to leave your phone is glorious.

Unfortunately on the 945 I find it randomly stops sending your text messages even though connected to bluetooth.

Frustrating

The barometric altimeter has been a weak point in many watches. I've had it break in one 920XT and 2 935's (and once a crack in the HR optical sensor too, but that didn't seem to affect the sensor). All were replaced under warranty, they all crapped out around 11 months!
The problem is is that there is a tiny opening in the watch for the sensor to be exposed to the air, if you swim a lot in pools, or shower with the watch, crystals can build up on the sensor and block it. One way to avoid this is to soak it in hand warm water with soap for 15-30 min every now and then (advise from Garmin UK). Personally, I've been looking at the 735XT because it doesn't have the barometric sensor and for my next watch I'll either chose a watch which doesn't have the barometric sensor, or one where I can switch it off. Where I live altitude isn't much of a thing, but you can't switch it off, so it's annoying when you log thousands of meters of elevation on flat runs and you have to go and fix that in garmin connect, strava and TP.

Garmin 935 and 945 are great triathlon watches. But 945 for battery life and I like the mail, music, maps for trail running, climb pro, Garmin pay, incident detection/safety, body battery, training focus, etc. But that are nor for everybody. However... Longer battery life means fewer charge cycles with same use. Watch gets, say, 600 charge cycles before loss of battery life (30%), so you are extending the life of your investment.

I have the 935. I’ve had it a little over a year and I have no need to upgrade, it’s the first watch with no flaws. At least from a triathlon standpoint. Music and pay would be nice but it’s not like it kills you to go the phone you should definitely be carrying with you anyway route on that.

With that said if I had to replace my 935 right now? It would depend on what my bank account looks like. The 945 is better, I don’t think there’s any question there. It just depends on if you need that extra $200. If you can afford it, I’d go for the 945 and “future proof” your watch an extra 2 years, and get the other features. If that $200 is a stretch the 935 from a triathlon standpoint has no shortcoming.

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I still lapped everyone on the couch!