Don't even bother with the 300. There is no PC connectivity, which means no uploading of detail maps and hence no autorouting. The electronic compass and other sensors aren't worth the money. They're just gimmickry and you'd be better served by the 500. When using maps, color isn't quite a must, but almost. I have a 400 with DirectRoute v2, and the maps are usable but would be much nicer in color. If you are on a budget, consider the 210. However, it has a monochrome display and you cannot add an SD card for more memory. If you purchase a 500LE, I strongly recommend purchasing the lithium ion battery pack. You can try to get it through Magellan or you can use the Motorola t720 extended life cell phone battery. The 500LE does not run long with AAA batteries and the included clip. Remove the clip and use the Li-ion pack.
Only the 210, 400, 500, 500LE, 600, and XL have PC connectivity. All of those units take an SD card except for the 210, which has a fixed 22MB of memory.
Thank you for the Info surly helps. I am new to this Geocaching so need lots of options and help.