Here are the key differences that I'm seeing:
101 to 201: charger instead of batteries (I can definitely justify upgrading solely on that), whistle to warn you when you are over or under pace, mapping of elevation (I live in Louisiana...there aint much elevation 'round here), autolap and autopause (whatever that is...), extra software.
201 to 301: monitors your heart rate, autoscroll (huh?), pc connection and website support, more precise GPS (how much of a difference does this make?)
301 to 205/305: it looks prettier, has 3 screens, and costs a bundle more (yeah thats all I got from the website).
So I'm thinking the 205 sounds about right. I like the plug it in capability so that I dont have to worry about batteries. I can't say I really care about my heart rate and I dont think I will use the website support all that much.
Does the tracking/gps improve drastically with each upgrade? What difficulties have yall had with the lower grades? Other than looking pretty (and being able to have 3 screens) what is better about the 205/305s?