I wouldn't really consider madoka a mechanic, rather, she's basically a bey car wash. The only thing she does to beyblades is clean them, shine them, and sometimes replace broken parts. She also doesn't have that much knowledge but basically just reads off her laptop.
Kenny on the other hand is knowledgeable, upgrades beyblades, fixes them, and is pretty smart when it comes to them (mind you, he gets real weird in the BEGA bit...but it doesn't take away from his geniusness). So in case you haven't gathered it from my post, Kenny is better by a long shot.
“In the course of twenty crowded years, one parts with many illusions. I did not wish to lose the early ones. Some memories are realities, and are better than anything that can ever happen again.” -Jim Burden (My Ántonia)