Can't speak for the Legend reception, but I own a Vista (almost identical), GPSMAP 295 and a old Megellan Skymap.
I use the Vista for geocaching and have never had serious problems with reception in even dense tree cover, if I keep the anetnna exposed. Sure, my EPE may fall to 30 feet, but that's to be expected. Keeping the antenna out and clear is important. If it's hanging down, hidden behind your body then you can expect problems. That's why a lot of gps have external antennas.
The gpsmap 295 has the best reception with it remote mount active antenna. With the little stick antenna it's a tad better than Vista. The SkyMap looses lock if you look at it wrong.
Honestly though, it's all in the antenna. When it's built in with no external jacks you do limit your options.