110 is very basic, no current pace, no programmed training. Just press start & run
210 similar, gets current pace, and supports foot pod.
Both are button paced, not bezel based. No wireless upload, USB based.
405cx, 410 both very similar, do all you need. wireless upload.
I've done a 35 mile ultra of 7.5 hours so battery life fine too.
405cx always comes with a hr strap, and can be had for 125 quid often.
410 can be bought without & with.
You've got 3 screens that you can flick between, 3 fields in each. Plenty enough. virtual partner actually is a 4th screen if used.
610 is touch screen based. Does everything.
But strangely is missing "course" feature that I've used during some long races for navigation. Not sure why.
Maybe see if a pal has a 405cx or 410 and get them to demo it, try using the bezel. It's easy to use once you get the hang of it.
Look here at dcrainmaker for reviews