So I am new to the site. I am looking to lift my truck. I don't know exactly what lift I should go with. A body lift or a suspension lift.

1st what are the pros and cons of a 4in suspension vs. a 4in body lift? I want to do the suspension lift but its a little more expensive. I don't want to spend more than 1k on the lift.
2nd what is the biggest tire size tire I could put on with a 4in lift using my factory 18in rims? I found a thread here where it says I could go up to 33 in. tires.
I now have factory tires now 265/65R18. I want to go with a more aggressive looking stance/tire. I live in Colorado and do a little bit of off roading. Nothing too crazy; mud pits, trails, and roads through pastures.
The "Falken Rocky Mountain ATS" tires have received good reviews from Discount tire, and come in several sizes.
Thoughts on these tires? I don't want to have to spend more than 1k on 4 tires. I plan on buying a used tire (of the same size of the larger tires I end up getting) on craigslist for my spare.

 

Suspension all the way. They make 1.25" and 3" body lift but they raise the cab off the frame. Don't really give you and ground clearance at all. If you want a lift under 1k around 4" then do the 5" rough country suspension lift. Great lift for the price and it's not to terribly tall. On stock 18s you could probably get away with around a 34" tire with some trimming