I use TomTom. I have the 310 at home & 510 at work. They are a little slow on updating the maps but if you're not driving through Springfield, VA or Austin, TX ... they're not too bad (LOL). One thing I've noticed is that sometimes you have to be creative when entering addresses (mailing address .vs. street address .vs. where the dang place really is (I used to live in White Oak which was serviced by Falmouth post office but had a Fredericksburg address - that sort of thing)

My siblings & I got Dad a Garmin for Christmas last year & he loves it.

IMHO: TomTom has better software & map detail. Garmin has better places of interest (gas stations & resteraunts). It boils down to personal preferences.