I'm a fan of both. Though in all honesty, the two complete each other. A Hitmonlee is without a doubt stronger, and with EV training and breeding, he's one kickass OTK for the party. Unfortunately, I have a problem with him. I'm a huge O.T.K. abuser, so I have to be prepared for a variety of Pokemon types versus my team. I can have this epic Hitmonlee that's owns everything in its path. But come to a Pokemon not affected by fighting type moves... He's in trouble. You have to switch him out for another in your party, which means your next Pokemon suffers a blow from whatever came its way. If you switch for a Shedinja, and the opponent sends a Fire Blast out of the blue your way, your team is already unraveling, all purely because of the moveset your Hitmonlee has you stuck with.
Hitmonchan, you have no way around it. You have to suck it up, and EV train him, because it's worth it. His versatility rivals that of Nidoking, Dragonite, etc. who are stronger, but lack the extra oomph. Let's face it. How many Hitmonlee have soloed the Elite Four? I've always managed to do so with Hitmonchan, not because of his stats; but because with his moves, you can set just that one Pokemon up to send the Elite Four packing.
My theory on Pokemon, and it's a harsh one. If your Pokemon is at level 80, and it still can't solo the Elite Four on its own, it's not worth training. They're just another collectable as you catch 'em all.~