Using two different pitched gears would probably be pretty noticeable if turning the gears with your fingers. When I set my gear mesh I always rotate the spur around a couple of times, 'cause there are some instances when I will have a slightly out of round one and I then have to try to compensate a bit for the side that would be tight.

Using two different pitched gears, one will try and grab a tooth before the other tooth is ready to go in to the groove. I'm not saying it's not possible to do, but I would think a person would be chewing up gears quick doing it.

The following video I watched while trying to figure out what pitch Redcat's gears were. It a little bit drawn out, but you'll get the jest of it:
https://www.youtube.com/watch?v=28umJU6J5kk