The youthful Xperia U is going to cost 259. As you should probably know already it will come with two exchangeable bottom plastic caps depending on the main color. The white Xperia U has white and yellow bottom covers, while the black version comes with black and pink accents.
The Xperia P is based on the same dual-core NovaThor U8500 chipset, but comes with a bigger 4-inch qHD Reality display with WhiteMagic technology, a better camera and more storage. There are no exchangeable parts on the panels though. This one is priced a lot higher than the U model 449.
The Xperia P retail price is very close to the first NXT gadget the Xperia S. Sony might want to consider it, because the quad-core gang is coming soon and it will give the Xperia NXT series a tough time for sure.