Well, the 205/305 are the older/legacy devices. That being said - I love mine...and can't justify the double price difference to upgrade to the 310/910
🙁 They are hard to come by now - Garmin has officially discontinued selling new stock - Costco/Sams might have them new. (205 = 305, but different color and no HRM)
If you live in a really rainy/precipitation heavy, the 310/910XT would be worth it. My under warranty 305 shorted out last week (battery) - Garmin has excellent customer service and shipped me a replacement via 2 day, but made me be a bit more conscious of drying it off after runs/quick wash. I've never had issues with it in the rain before, so think I just got unlucky. (And/or it hadn't truly dried off before I put it on the charger to charge)
310xt = the new version of the 305, water resistant to 50M. Not truly a water/swimming watch, as it only estimates distance traveled.
910xt = the true triathlete's watch - measures actual distance, stroke rate, pool lengths, etc.
In regards to an everyday watch - none of the above would be suitable for an actual watch to wear around really. IE, battery life would prohibit it from a length standpoint, not to mention constantly searching for satellite signals (if inside). I wear a watch 24/7 (in the shower, in bed
😉, etc) - I don't find it a huge deal to swap watches in the morning. I had the same thought as you about wearing it as an everyday watch - initially when I started running, I bought a Polar RS100 HRM watch. It was great in that it was waterproof, could use as an actual watch/replacement for my G-Shock, was on all the time, and had a HRM. It sucked as a running watch though, because you honestly don't know how fast or far you are going, or can't realy truly analyze mile splits/times later on.
Honestly though - the GPS watch is the single most effective training tool you will ever purchase, and it pays for itself. (It costs what 1-2 pair of running shoes cost, or multiple pair of shorts, etc) My first Forerunner 305 lasted me 3.5 years. It was having a hard time finding a satellite at times, so sold it and got another 305 in Dec, which just shorted out. Replacement so far worked well, at least in today's 10 mile sweat drenched tempo.
🙂
NOTE: there are some running purists now that are anti-GPS watch - they think we've become too reliant on technology, knowing every stat, etc. I still go out on easy runs with a normal stopwatch and run based on time, but for actual half/full marathon training, it's invaluable. You can upload your runs/stats to MapMyRun.com, Garmin Connect, or the other lesser known sites. (RunKeeper, RunAhead) If you're a numbers/statistics geek like I am, you'll enjoy the fact that you can analyze it.
Ex, here is my NYC Marathon route from November:
http://www.mapmyrun.com/workout/76582888