aaah the almighty GPS, I have owned all sorts, garmin 12, foretrex, etrex, magellan, and have recently upgraded to the 60csx.
My conclusion was compatibility with my laptop, mapping, durability (i.e weather, snow, rain) and I really like the 60csx for it's enhanced antenna. I've recently used it in the jungle, and was very pleased, having picked up 5 satellites, and my buddy was standing 5 feet away and using a etrex vista cx, and had no reception.
but it boils down to pocketbook...and like I tell my students, what is the best compass and gps in the world..."the one your most proficient in."
best of luck
Eric