Exi, I think you are mixing things up here. wheel spacers move the rim way from the brake rotors. Coil spring (aka, lift) spacers lift the tire away from the body.
As for pros and cons. The pro is that for little money, you can get a small amount of lift. The con, you are going to be more likely to max out the travel of your suspension, which is where damage can occur. If you are only staying on the street, this is quazi acceptable as I see it due to minimal amount of travel. This is really only a problem with the front end of the truck. If you are looking to go out 4x4ing, I wish you luck.
Also keep in mind that with the added spacer, you are putting the front end components at higher angles. Higher angles means the components are going to wear out faster and they are going to transfer more road noise to the inside of the truck.
If you do this modification, getting new shocks is highly recommended as I see it. that way, you are less likely to hurt something on the truck. I don't know if you have seen what a shock looks like that has been pulled on too hard, but it is not pretty. That is what you are going to end up doing if you keep the factory shocks on the truck. The next component to take the abuse will be the upper and lower ball joints on the front suspension. If one of those fail, I am sure you can imagine what is going to happen there.
I am not trying to scare you. Just trying to make you understand why things cost what they do. There is a reason why a lot of lift kits come with tons of new suspension parts that need to be added.
As for whether to do 2 or 3" spacers, if you only do 2's, you are going to wish you did 3's and either way, you are still pushing the suspension components to their limits. Just with the 3's, you are more likely to hurt something.
