Racing wheels are light, quick, aerodynamic.
Training wheels are cheap and durable.
It's a difference in expectations. Training wheel quality is measured in miles. Racing wheel quality is measured in weight and coefficient of drag. And after all that, besides the cost difference, if you race, you will want a minimum of two wheelsets: one to put on your bike, the other to put in the wheel car or wheel pit during a race. The training wheels typically act as backup race wheels.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter