I too have a 3320 and I bought the CX and a 4 n 1 bucket for the front -that was pricy ,but know that I've had the 4 in 1 ,you couldn't get it away from me.
I had the same question - and was shown - the cylinders on the loader is the only differance between the 300,300X and the 300 CX to give the extra lift.
Jan 7th of 09 I bought an 2008 3320 tractor 0 hrs:
In Langley ,BC ,Cnd - I paid $20,083.00
I added 300CX loader for $4188.00 which came with a 72" bucket.
I added a 4N1 bucket for $2699.00 which came with a 60" bucket and needed to add the power beyond kit for $362.00,to run the hydraulic's.
The 4n1 bucket takes you from "just" a loader to an I can do anything!
I built a boom that I drive up to and close the mouth on and I'm a crane ,did the same with forks, you can bulldoze, clam ,bottom dump, ...it's just the most usefully tool.
Good luck.