https://buy.garmin.com/us-us/us/p/560327

As for the features, at this point you probably have to sit down with the manuals for both watches and really deep dive the features, and even then the manual usually doesn't cover every little feature/option. I remember reading that the 735XT had quite a few "hardcore" fitness functions that the Fenix 3 HR did not, but they may have added those to the Fenix 5. That would surprise me though, Garmin is the king of not offering everything in any single product even their top of the line. So I'd be surprised if you get EVERY fitness function that the 735XT offers in the Fenix 5, just like I'd be surprised if you get every navigation, waypoint, etc. feature on the 735XT that you get in the Fenix. Garmin is very good about restricting just enough features that if you want everything for running, cycling etc. you will buy their specialized units.
I remember reading that the 735XT had quite a few "hardcore" fitness functions that the Fenix 3 HR did not, but they may have added those to the Fenix 5. That would surprise me though, Garmin is the king of not offering everything in any single product even their top of the line. So I'd be surprised if you get EVERY fitness function that the 735XT offers in the Fenix 5, just like I'd be surprised if you get every navigation, waypoint, etc. feature on the 735XT that you get in the Fenix. Garmin is very good about restricting just enough features that if you want everything for running, cycling etc. you will buy their specialized units.
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I'm not sure it covers everything but the 'compare' function on the Garmin web-site makes it quite easy to see what functions appear where, see here for example. Although if the 735XT is anything like the F3 was it may have gotten a load more functionality since it was released.
Which hardcore features are you referring too? The only features I can think of that the 735xt has over the F3 is Varia support, Strava segments, next gen CIQ, and Garmin supported TBT navigation. In fact the 735 lacks several important features that are available on the F3 (i.e. altimeter, multiple bike profiles, Virtual racer, tempe support...etc)
I use an Edge 1000 as well, and off the top of my head the Edge 1000 offers a few things over the F3
-TBT directions directly from Garmin Connect
I got my F3 on release in early 2015, and it has been on my wrist practically 24/7 except for charging. The amount of functionality added for free through FW has been great too. The F3HR wasn't enough for me to upgrade but the extras the F5 bring along with the wrist HR and a renewed FW up-grade cycle make it a must buy (as long as the UK price isn't completely silly).
That's actually not the case any more; Connect started sending courses with TBT embedded to the F3 around October last year. Great list, though.