What cassette you get for racing wheels depends on what racing you will do - crits, road race or time trials, and the terrain for each. You are not going to want to be shifting a compact between chainwheels much in a race (personally I would not race on one) so don't go too tight. Besides, with 10 cogs you have some room to go larger. Keep in mind that for decades racers managed to go fast with 5 cogs in the rear and downtube shifters. To retain some hill climbing ability and still keep the gears close I would think an 11/28 or 12/30 would be fine, but if you only race flat crits you could go tighter. Again, it depends on your fitness level.