Here is why I was thinking that the Oregon is using a new antenna.
http://garminoregon.wikispaces.com/Hardware
I can't seem to find any information on the exact type of antenna, so if anyone knows jump in.
Back to the OP:
I am told that the GeoXT is a great little unit, but to get the sub meter accuracy you need to post process the data. Which usually means you have to buy post processing software in addition to the unit. Post processing software can be VERY technical. So there is a big learning curve when you get into this type of software. There are things like setting up the proper coord system, manually adding your Geoid files, proper operation of the data collector and PP software. All of this takes time to learn and may add an additional cost to training when it is all said and done.