[n33k0]

From what I understand:

Spindles are preferred because they don't change the suspension geometry, they just move the wheel up in relation to all the suspension parts. You won't have to change your shocks with spindles, although I don't think you would need to change the stocks for a 2" spring drop either. Using a spindle gives you the option of adding drop springs later to go lower without running into the regular alignment problems of going with extreme drop springs from the beginning(if you want to do that)

Edit: As a con, I've read that some spindle/15" wheel combos might have rubbing issues (spindle rubbing the inside lip of the wheel)