RR,
Can't speak to the duability of the Meridian, but I can to the Garmin units. I was involved in a trail program with the USFS several years ago mapping documented and undocumented trails in the Santa Rita Mountains of southern Arizona. We used Garmin GPS III on Quads and Dirt Bikes and had "0" failures of these units over the 1 year that the project lasted. To say that they got the occasional "Bump" would be an understatement, we beat them up pretty good. My III+ is still going strong and only now is it finally being replaced by a 60cs. I think I will still keep the III+ as a back up. Go with the "V" if you don't want to spend the extra money for the 60 series. IMHO
Rick B.