Absolutely buy a 4x4. Not only will you be kicking yourself slipping down the ramp, but everyone will laugh at you.

4x4 all the way.
First time you hit a ram that's wet, slick, or sandy you'll appreciate it.
One local ramp is steep and many truck have trouble pulling boats up and out. I drop mine into 4x4 low and out it comes real easy.

No question 4x4!!

Definitely 4x4.. I had a 2 wheel drive truck before, but got tired of smoking the tires to get up a slippery ramp and bought a 4x4....

If you don't get 4wd, you will be sorry the first time you get stuck on a wet ramp. The only time I ever use 4wd is on the ramp, but it is worth it. Go for it.

4x4

Believe it or not, duallys have less traction. I did not believe it till the first time I went to haul out, barely touched the peddle and wheels spun! Get 4X4!!!!!!!

either a 4x4 or put a winch on the front of the 2wd

I must be real lucky.

I've towed and splashed the following with a Ford F350, 2wd, crew, with not 1 problem:

30' Scarab Sport
302 Formula
Gun
50' Nortech Cat
50' Nortech V

Did have Limited slip and ramps were in good condition.

I've never had a problem on the ramps either but i've seen a couple 4x2 super duty diesels get stuck on wet grass