Personal preference and Void's summing up of the psychology behind it are what I think. It happens in lots of trick or performance orientated things - In rollerblading I always felt more confident to jump substantially higher with 10 grams lighter boot, almost as if slightly less lightweight skates would inhibit me from reaching my potential. Although in theory an element of truth behind it, I built up in my head that one skate would make me jump higher than the other. Whereas if I didn't know the weight differences, the end result would have been neither here nor there.
The differences between kendamas are much more subtle, and if you trained two identical twins up one with a mugen and one with a tk 16 (neither having background knowledge of the prices/knowing the hype), there is no way you could guess who would become better. I got my first and only mugen in 2008, and then decided that oozoras were much better as I learnt my "cooler" tricks on them at the time. Do I regret my decision? No. Although, it would be nice to have a few hunndred quids worth of toys to sell to magic believing children when times get tough..