auto start/stop is a setting... if you turn it on.. it automatically stops (or starts) the computer when you stop (or start riding)... sooooo if you stop at a long light... your timer doesn't keep going.. cuz it's not ride time... or if on a ride and you stop to rest or at a sag stop... the computer stops... then starts up again when you take off... that way your stats are all RIDE time... filtering out the rest time...

with the 725 (which for some weird reason they left it out.... didn't get an answer way back when when i asked to polar guys about it at a both) but anyways.. the 725.. you either have to manually remember to push the button to stop at a rest stop... then remember to push it again to start the timer (ya.. like i'd remember to do that!?!?) or your computer keeps on recording time... so say you ride 1 hour... stop 10... ride another hour... when you get your stats.. it will show 2 hours 10 minutes of time passed.... and also get your heart rate (if you are close enough for it to pick up) for that 10 minutes you were stopped.. rather than just averaging ride HR...

(one thing i think is going to be really cool with the cs200... it has "time to destination" or something like that... so, for example... saturday i will put in 114 miles... and it supposedly will tell me that i have X hours til i reach my destination based on my current speed.... i think i will have fun with that (or i will get depressed! especially when climbing at 4 mph and it tells me 4 days to destination! lol! the 720 doesn't have that though! just the cs models!)

definitely make sure you look at the comparison chart at polar.. and get the one that has the most... most IMPORTANT features you need and want!

(editted to add: if i remember correctly... the only difference between the 725 and 720 other than the way cool casing of the 725... no auto start stop on the 725... and you can upload the info from the 725 to certain phones... other than that.. yes... i think they are identical! but to me, personally... the auto start/stop was a big deal!)