I've had my L4400DT for a few months now. When I was looking at them at various dealers I never saw a two wheel drive and I did a lot of looking.
If you're unsure of which one to get, don't be. Get the 4WD. I've been doing a lot of heavy loader work and the terrain on my place is very hilly and uneven. The 4WD is indispensable for me. If you have flat fields, good traction and don't plan on FEL work, then it may not be worth it. Otherwise, I think 4WD is the way to go.
On a side note, the 4400 is my first tractor and I'm new to tractors. Did some 'farmhand' work years ago on big old tracotrs but that's it. But the 4400 has exceeded all my expectations. I could not be happier. The 45 hp allow me to pull a big old 7' heavy duty single spindle rotary cutter with no problems at all in waist deep fescue, blackberrys, dog fennel with plum and locust mixed in.
My 6' JD LX6 balances perfectly with the FEL on and it handles it with no problems too.