I looked into this earlier in the year and went for a Magellan Explorist XL. Having a half decent screen swung it for me over the garmin stuff. Not the best for sunlight viewing and the chart could be better. otherwise a very nice unit.
We bought a Garmin after we were lucky enough to borrow one and try it first. Pretty accurate (used it in the car, compared sat nav, speedo and garmin), and the battery life is as good as the batteries - use decent ones.