^ yes it does get around that. Obviously it's more convenient if they can run at the same speed, as you can then control more than one module using the same train controller. You also don't need to remember which speed each of them runs at if they'll all run well at full speed!
Well, another day, another module! Unfortunately I'm rather running out of M motors - I only have one left! So I decided that as I made a small Sweeper module a couple of weeks ago which was specifically designed to connect to other modules, I'd make another one which utilised this function, so that I didn't have to use my last M motor!
As someone who will shortly take my first faltering steps into the GBC world, can I ask why you use M motors, as opposed to L or XL? A number of the GBCs I've seen online seem to use XL motors for even small modules. Does it matter which you use?
Mainly because the M motors are a lot cheaper! I also managed to get 8 of them for £1 each a few months back, so I had quite a surplus of them.
As others say though, in most modules there's really no need for anything faster or with more torque. In fact most of my modules are geared down so that they're slower than the motor runs. I've only used an XL motor in one module (which isn't finished and probably never will be), but even then its entirely possible that using an M motor would be fine.
I can see why complex modules (such as Akiyuki's Ball Factory) might need something with a bit more torque, but I've not built any really complex ones yet. For normal modules, M motors are fine.