Yeah, I suppose it'd be better to use HMs if there were some variety in the typing. (Seriously, Fighting, normal, Water, and Flying. That's it. And please, who wants to use the weakest Fighting-type attack in the game?)
Also, HMs are unlimited in uses, but can only be forgotten by a Move Deleter. This tends to be tedious if you want to teach your Blastoise Hydro Pump, per se, but already have Surf on him. In that case, you need to stop learning Hydro Pump, delete the move with a Move Deleter, AND get a Heart Scale to remember Hydro Pump, which is extremely frustrating.
Do not worry, my friend: GameFreak has done a great job giving Pros and Cons between TMs and HMs. =)