About the same, actually....
There are basically two 33" tire sizes for 15" wheels. the 33x10.50 and the more common 12.50 width... but they're load range C. which will net your a more flexible tire offroad with lower pressure. For 16's you have 255 85 16 and the 285 75 16 I think both are available in E rated, while the 285 is C, D, and E rated.
If you have the cash, and intend to use the truck offroad a lot, check out the Interco tires. I'd love to fit 35 x10.50 Super Swamper SSRs or even the 34x10.50 LTBs. But alas, I don't really need them for what I do. But they'd look pretty dang cool.