If you need gps based training data, garmin has a near monopoly position in the market, so you really don't have much of a choice other than picking either the 500 or the 800.

But in this day and age of $199 Kindle Fire and high res color display in $200 smartphones phones (unsubsidized), it really is a shame that garmin can't do better than these two devices with better display and better CPU and software. So from that perspective, none of the garmin devices are worth the money.