I've got a boatload of batteries and a GPSMAP 76S, which is similar, just higher drain than the OP's Vista. My two main sets of batteries are powerex 2700's and Eneloop 2000's. For just about everything, the Eneloop ends up being the better battery except things like my GPS.

The Eneloops seem to run at a slightly lower voltage, kicking out low battery warnings way too early, plus the obvious fact it has significantly less total capacity. If you're used to swapping batteries at least once every two weeks anyway, the higher capacity Sanyo or Powerex 2700's are going to be better for the GPS than Eneloops. Same for primary lighting. For blinkies, TV remotes, wireless keyboards and mice, etc. the Eneloops are the way to go. GPS & primary lighting, the higher cap cells are better IMHO.