Second to what wgority said. The smallpipes are nice to have, and you'll want them at times when you don't feel like playing the uillean set. I love my smallpipes - I've got them fitted with Song of the Sea brass drone reeds, and when I strike in they sound like a swarm of bumblebees.

Also, he's right that you won't make much of a dent in the cost of an uillean set for the price of a set of smallpipes.