I researched my brains out on this very subject. I agonized over it. It's easier picking a wife then it is an electronic gadget.
I wanted the Quest very much for the voice activation (the eyes, getting older). Plus great price ($350) that included City Select 7. I trusted it to handle my outdoor use.
I choose the Garmin 76c Because.
Rechargeable replaceable batteries which I like in all my devices.
If I don't use the device for awhile I don't have to worry about keeping a charge on it, just take out the batteries.
I liked the feel and handling.
Fits with in case for clipping on belt.
If the Quest battery goes, then there goes $100 to get replaced plus shipping etc.
Also the Quest speaker is in the power cord, spill your coffee on it, or goes bad, another $70. I figured both would happen over the life of unit. So that pays for the 76c. Also concerned about outdoor use with flip up antenna (maybe get snagged and break). I admit that I have not actually handled a Quest, but I got tired of picking it to death.
Just ordered the 76c today ($489 total for receiver and maps). Even though I haven't used it yet (I have never used a GPS receiver) I feel confident with my decision.
Hope this is food for thought. Jim