If you're going to be 50 miles from home it's nice to have the ease of fixing a flat by just sticking in a new tube. If you are thinking of racing seriously, tubulars are good. They are more trouble to mount but when glued properly, a flat at high speed in a pack will not cause you as much grief; when a clincher blows, it is often instantly, and rolling the tire off the rim in a corner is a possiblility. Tubulars tend to leak only from the puncture instead of all around the rim so you may get some time to stop safely. You can ride the flat to a stop most times because the glue holds the tire in place.
Personally, I ride clinchers on the road, but use tubbies on the track. A half decent pair let you run pressures of 150-170lbs. which makes you pretty much float on the track surface. You're never far from home, so flats aren't so much of a problem and getting down off the banking with some rubber under you instead of just a metal rim is nice.