I have an Sportrak Map. Nice unit, the Meridians offer the SD card use with seems like a great idea. Sounds like they work fast if you use a card reader to transfer data.
I've had an old Garmin 48, which I gave to my brother the boater, when I got the Sportrak and one of my hunting buddies has the etrex vista.
I love the big display on the Magellans. My unit picks up enough satellites in the house to get a 3d reading where the Garmin 48 wouldn't.
The menus on all the map capable units are pretty easy to use. I think the Magellans are easier to read. Just got my son-in-law a Garmin RINO 130 and it is a nice little unit, but that little is part of the problem. The screen is really little.
The Magellans float if dropped. I have dropped a radio into the Colorado River that was clipped to my shirt pocket. Floating would have been good.
I liked my friends etrex vista. Two negatives. Hard to read screen and the antenna didn't work very well when under a tree canopy. In fairness, I have not had this Magellan in that same type of forest yet. But I'm reading that others are finding the Magellans to be better under a canopy than the etrex.
And my wife upgraded me to an explorist from Costco when they first came out but I had to return it because it had no pc interface. The newly released explorists do. Don't know what the marketing dept at Magellan was thinking!
Looks to me like the Meridians are the best bet because of the memory cards and big easy to read screens.
The proprietary map requirements are kind of a rip off. Like the PC or Mac worlds of the eighties. Maybe one of these companies will have the guts to open the code to other map writers. They'll sell more units if they do.
Good luck, I always thought I'd stay with the Garmin lineup, but I must admit I really like the Magellan Sportrak and the Meridian looks like a logical refinement of that idea.