I'd say pullies because 1)they are cheaper, 2) they do alot for our truck, 3) easier to change than x-pipe (personal experience). Don't get me wrong, the x-pipe is worth it because it does add some ponies but pullies are always a good upgrade.
The pulleys are cheaper than the x-pipe and you'll get more seat of the pants difference from them.I recomend going with an off road x-pipe if you can get by with it in your area but the pulleys are a popular mod with a well deserved reputation in the "bang for the buck"category.