I love my Garmin 935XT, and the Garmin 920Xt before that. You can get refurbed 920Xt really cheap, these are great watches, especially is you ever cycle or swim a little, want to do a longer ultramarathon, or record long hikes.
Be aware that although Garmin and Strava will both give as estimated elevation gain for all watches, only some watches actually have a barometer to measure altitude. This makes a big difference if you live in rolling terrain. The Garmin 735 doesn't have the ability to measure altitude, the 735 and 935 both can. I am not sure of the 235 series.
Optical HR monitoring is basically useful for working out, so i woudln't put much weight on that feature. Their biggest use is measuring HR through the night to get an idea of RHR. When exercising the chest strap is much more accurate.