I have the Garmin, and haven't tried the Sporttrack. (Amazon had an additional $50 off last Christmas so it had an unbeatable price!)
I have had only positive experiences with this unit. NiMH 2100 mAH batteries last about 6 hours of continuous use. I use the unit to interface with a radio for ham radio position reporting and it works great. I've had it out back country hiking numerous times--it's durable!
All functions are easily accessed and used. I needed the manual only the first few times using it. It locks on to the satellites pretty quickly and keeps the lock reliably.
The map isn't street level but is detailed enough to give major cross-streets (which helps orient myself to the caches quickly). The map zoom is easily accessed from side buttons.
It seems to be pretty dust-proof, I haven't had any issues from working with it in extremely dusty conditions (desert).
Good luck!
