I have fired tens of thousands of rounds (probably around 10k through one and around 30-40k through the other) through two Surefire X300s. I own an X300U, TLR-2 and TLR-3 though I haven't fired nearly as many rounds through those two lights. Each year I see hundreds if not thousands of deputies and recruits pass through our training with Surefire X300, X300U, X400, or Streamlight weaponlights. Yes, crap will get on the lens, but there are a couple easy fixes. Number one, clean frequently with a pink eraser. Option two is to dab a little bit of Froglube or SEAL1 paste on the lens (non-petroleum based) prior to shooting. Then wipe it off and re-apply.
When it comes to weaponlights it is all about what you want to do with the light. The duty-sized weaponlights such as the X300, TLR-1, etc. balance run-time, output, manipulation, and size. Two batteries offer higher voltage, more capacity, and consistent footprint so accessories such as the contour switches and Surefire DG switches will interchange along the line.
Most compact weaponlights aren't truly compact, or don't function correctly for what a compact pistol should do... carry concealed. I have followed and worked with these lights since the old Insight X2 and am currently trying to obtain some different options for testing.
I would prefer to get some more information before I try to give you a detailed suggestion of a light. Do you carry the pistol? Is it concealed or duty use? Is it for home defense? Do you shoot with a "thumbs-forward" grip? Would you want or be willing to use pressure switches or do you want the switching to be self-contained in the unit? At what ranges do you want to be effective? What is your budget?