@kevin, I have the 735xt and highly recommend it. I used an apple watch for my first 70.3 and numerous marathons and the battery always died. I switched to the Garmin last year.
First off, if you haven’t already, here is a full review from DC Rainmaker that is really good. https://www.dcrainmaker.com/2016/06/garmin-forerunner-735xt-in-depth-review.html.
- I sync it with a Wahoo chest strap HR monitor (ANT+)
- Sync to a Garmin cadence & speed sensor on my bike (would be the same for a Wahoo since they are ANT+)
- Swimming – I don’t think it auto-laps, but it auto tracks distance & stroke rate based on what lap distance you set it to (ie 25yd or 50m). It has lap button you hit between sets and it switches to rest, the you hit it again to start a working set. its pretty easy functionality & the data comes out nice in TrainingPeaks, Strava, Garmin Connect…
- Zones – you can set all your custom zones for bike & run on the Garmin website or app & it will sync to the watch. Each one of those activities will have a HR zone screen to tell you which zone you’re in
- Price – I got mine of amazon for $235 (https://www.amazon.com/gp/product/B01DWIY39A/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1)
- Battery – I charge mine once or twice per week, but the battery using GPS lasts 12+ hours. It charges up from 0% to 100% quickly too (under an hour)
- Custom Workouts – I like building out all my interval runs & bikes on it and then the watch guides me through the workout and tells me what zone to be in. This is a huge plus for me
- Brick & Tri Function – The watch was built for a triathlete in mind since it has a workout setting for brick & tri. This will let you start the workout once and then it will track your first segment, transition, second segment, etc…. I find it beneficial on race day to easily track the whole race without worrying about switching the workout mode your watch is in.
Hope that helps