735 should be, HW wise, better than 235....If you can afford 735, go for it, but otherwise 235 will do either.
I've had 230, now I'm on tomtom spark3 cardio music, good device, but I miss garmin's color screen, and better ecosystem...Still, I don't need my phone to stream the music to the bt headphones...always some compromise has to be made
I've not had any issues with the 235 battery life. I just charge it after a run while I'm in the shower and have never had it run out with HR enabled all the time. On days where I don't run it only goes down a few %.
On really long runs I just turn bluetooth off for those and it's fine. You can turn the HR off too if you really need to, but I've never needed to. I think the longest day was somewhere between 5 and 6 hours of running and there was still battery left at the end. I think I turned bluetooth off for that, but HR was enabled the whole time.
I have a friend who's 235 runs out of battery every now and then, but that's more because she doesn't charge it particularly often
The only difference is the optical heart rate. You can use a heart rate strap on both of them, but you may find those annoying to use.
So if you care at all about heart rate or think you might do in the future, go with the 235.
If you don't care about heart rate or think that you'll be ok with a strap if you change your mind in the future then the 230 is ok.
I hadn't seen this thread but I just made this choice and plumped for the 230. Mainly because it was about £50 cheaper on Amazon and I hate spending money on kit, but mainly because I rarely use HR, I have a strap if I want to use it but I can't see it getting much use. It looks like things have moved on a lot since my 305.