I am trying to decide between the Garmin 245 vs the Apple SE. Whichever i purchase will be used with Strava, running, biking, and (ideally) open water swimming.
I have done some preliminary research. It seems fairly evident that the Garmin’s GPS is superior and that would be the most important feature to me, but another important one would be live tracking.
I’m sure both watches do expected things adequately, but i’d appreciate any experience others can offer. Thank you in advance.
Garmin makes exercise watches that have a few smart features. Apple makes smart watches with a few exercise features. Considering you’re on an exercise forum you’re gonna hear a lot of Garmin around here.
Apple dramatically improved GPS accuracy with the current generation. But I do not know if that carried back to the SE line. If you use a power meter on your bike, then Apple does not natively support that. (There is one 3rd party app that supports bike power meters.) Live tracking generally requires a phone with you, so all devices are equivalent in that regard. To get independent live tracking, you would need an Apple Watch with cellular or a Garmin 945 LTE. And activity data sharing to Strava is a little clunky on an Apple Watch.
Here’s a quick list of the things you give up on an Apple watch relative to a true sport watch:
Odd “segments†& “laps†splits data structureSwimming cannot manually start & stop interval lapsNo ecosystem of adjacent products & features – highly fragmented app environmentLimited vertical platform – no web and basic phone UILimited screen and data field tailoringNo performance analyticsNo accessory device support except through 3rd party appsNo “Daily Report†type feeds (possible “with an app for that,†but even more fragmented)Touchscreen UI accidents - touch just does not work as well and easily as hard button watchesData sharing semi-manualShort Battery lifeNot really always-onBasic & tedious structured workouts - doing this on the watch is a royal PITAActivity start countdownHeavy - its about 50% heavier than most race-oriented multisport devicesNo mapping Edit: Your post mentions the 245, but you ought to consider the 255 - it is a quantum leap forward from the 245.
I have had the Garmin 935, Coros Pace 2 and now I use my Apple Watch (4 and now a 7) for all workouts. It really came down to having one watch to do everything, since most of the apps I use have Apple Watch apps. If you are already in the Apple ecosystem then it’s easy to just use the Apple Watch (I use Training Peaks and 2PEak etc. etc.), so if thats you, I say go with the Apple Watch, although I am not sure about the SE rot be honest. From what I recall it is missing some features that may be important for endurance training and racing, but don’t quote me. 
I have had the Garmin 935, Coros Pace 2 and now I use my Apple Watch (4 and now a 7) for all workouts. It really came down to having one watch to do everything, since most of the apps I use have Apple Watch apps. If you are already in the Apple ecosystem then it’s easy to just use the Apple Watch (I use Training Peaks and 2PEak etc. etc.), so if thats you, I say go with the Apple Watch, although I am not sure about the SE rot be honest. From what I recall it is missing some features that may be important for endurance training and racing, but don’t quote me.
Battery life for one thing.
You mentioned using Training Peaks with your Apple Watch. Can the Apple Watch show custom Training Peaks workouts in advance? So if you have an assigned workout with intervals, the Apple Watch can tell you the intervals as you’re doing the workouts? Garmin can do this but wasn’t sure about Apple.
For an Ironman probably but for a half should be no problem. Of course now they have the Ultra which they say can last an entire Ironman.