Personally I'd go with the 4" suspension lift over the 3" body lift. Yes it's more money, but it's the proper way to do it IMO.
For 4" lifts Rough Country is the cheapest. But what I don't like about their 4" kit is that it uses a rear coil spacer rather than lift springs. For that reason I recommend the Zone kit instead. It comes with 3" lift coils for the back instead. With either kit I would also use Bilstein 5100's to properly level the truck with the lift.
Now that being said. The price difference to go with a 6" kit over a 4" kit is very minimal. $150 of a difference in the Rough Country kits.... So I recommend spending a little more money and going with the 6" kit. You'll probably end up regretting the 4" kit down the road wishing you had gone higher. For the small price difference you might as well doing it right the first time.