Haven't used a new optical arm strap (seriously considering pre-ordering the Scosche 24). However, I have noticed that indoors, on the trainer, steady state, reasonably tight watch HR monitor is actually quite accurate (checked against palpation) within a few beats. Also resting HR when you wake up reasonably accurate. HR sitting at a desk reasonably accurate. However outdoors in the sunlight, or any increases in HR such as intervals or even a teeny tiny hill and the wrist monitor is pure garbage. I mean it's almost as bad as nothing at all. Chest straps are still considered the gold standard but sometimes need a bit of help from a dollop of electrode gel especially if you're like me and own a bunch of cheap stuff. I've had plenty of odd spikes at the start of a workout before I started using electrode gel. If you live in a dry area or are in a drought it might prove to be hard to get a good reading. Basically what I'm trying to get at is the right tool for the right job. Eventually I'll stop being a cheap skate and use all 3 types of monitors. Wrist based is great for steady state on the trainer or the ability to check you resting HR throughout the week and know when to take a day off. The chest strap would be best for cycling (especially if you have a bunch of long rides in a row), or as a back up when you don't charge your arm based HR monitor, plus all in all is still king of accuracy. You arm band is great or running and everyday use.

---

I still lapped everyone on the couch!

My Scosche optical works great for bike and run. Most importantly though, it doesn't die a 6-month death as literally 10 Garmin HRM straps I've had have died in the past (all of them replaced once under warrantee, so I bought 5.)

The key is to cinch the Scosche super tight. You can't get the Garmin wristwatches with built in opticals as tight.

I actually still have a separate Garmin HRM strap now but I now reserve it only for races, as I'm afraid I'll lose the Scosche in the OWS with my sleeveless wetsuit (almost happened once!) But since the Garmin HRM strap dies within a year without fail, I stick to the Scosche for training. Mine is going solid 2 years no problemo,with the reads as good as day 1.

Wrist based optical is pretty well known for getting cadence lock--- where the bpm equals your cadence. Any chance your run cadence is in the 155-160 steps per minute range?