I own and use both (LP400 Carbon) on a regular basis and they both bring home the bacon if I do my bit. I would be hard pressed to say which is the best. It all comes down to personal preference. What I can say is that I recently sold a Steyr LP10 because I didn't get on with it as much as the LP2. I do find the LP2 uses more air and requires regular barrel cleaning to maintain accuracy.

HTH
Ian