dmg

The important thing is threads per inch (TPI) - it will make the casing more solid which will dramatically improve the cornering and generally under high-stress situations. The downside to this is cost and to a lesser extent durability (most cheaper commuter type tires are 60 TPI or thereabouts, which is fine for normal riding around situations). max PSI is also important if you're looking for speed, although it'll make for a harsher ride. I would recommend Continental Gatorskins as the best of both worlds - they're 170tpi, can go up to 120psi (well, the 25mm ones can, anyway), have flat protection, and you can get them for $40 or less.