Here are the Pro's and Con's of each.
3GX, cheapest of all of them. 3.0 is crap, but 3.1 is great. Must have a computer to do most of the setups beyond the basic setups, but you can fly quite well with teh basic setups.
AR7200BX, No computer needed. All setup is done on the gyro and with your Tx. Can get confusing, but following the instructions can get you in the air pretty quickly. I watched as Matt set his up and I think it took about an hour the first time. Only issue was the gyro was reversed as seen on the video when he stripped the tail gear.
IKON, this is the best of the best. You are just now starting to do your orientation and soon, you will flip that bird inverted for the first time. This gyro has self leveling and all you have to do is flip a switch and it will flip it right side up and all you have to do is add collective to keep it in the air. You need a computer to set this gyro up.
Then there are the APS systems. We are talking about >$500, but use GPS and are a true hands off system. I'm sure you don't want to go that far though lol.