I can't tell you all the differences between the 220 and 320 right off the top of my head but I have both. I bought the 220 and a dc30 from a guy that was getting out of hunting just so I could track more dogs while hunting with a group. I then bought a 320 with a few dc40's. The 320 had more features and is an all around better unit. The 220 will track 30's and 40's but will not track the 50's. The 320 will track 30's, 40's and 50's. The biggest difference I found between the 30 and 40 is that the 30, with the top mounted GPS receiver keeps satellite reception better than the 40. The dc50 collars are, in my experience, far superior to the 30 and 40. Garmin went back with the top mounted GPS receiver but also added the capability to track from around 28 additional GLONASS satellites. They have tough,long range antennas from the factory along with an additional shorter antenna in the box. They have better range,less interference, and when you add in the bark detection, rescue mode, and longer battery life, you start to see the advantages. I now have four 50's and keep the 30 and 40 for backup and loaners. For me the 50's win hands down without a doubt.
The newer 320 comes with the updated software to track the 50's and the older 320's can be updated if they don't have the current software. More people are starting to use the 50 collars and if you have a 220 you are left in the dark if you hunt with people that use them.
As far as long range antennas, a good truck mount antenna will increase your range dramatically. I use the truck mount until the dogs tree then put the small antenna on when heading in on foot. The 320 comes with a long and short in the box.
With the price of a 40 or 50 plus the price of a Tri-tronics collar and transmitter, it would be cheaper to go with the Alpha and TT10. I went through the same debate and I use dc50 collars with Tritronics. The ONLY reason I went that route is because I became accustomed to the bark detection feature on the 50's and just can't bring myself to let it go. If or when they make it available on the Alpha I'll likely change over. It's just so useful. If the garmin shows the dog treed but not barking, it helps you better understand what they are up to. They could be resting, hung up or injured. On the other hand, if it shows the dog moving slowly but barking a lot, like with a walking bear, it's nice to be able to have that info available.
In my opinion you can't go wrong with the 320 and dc50 or the Alpha and I would steer away from the 220.
