[BP-Revo]

I have a cordless one and I get by with two batteries. Having just 1 battery SUCKS because when it runs out you have to wait like half an hour for the battery to cool then another 3 hours for it to charge. Really hampers your ability to finish your projects. But after getting a second battery it really helps. One is always charged and I usually finish whatever I am doing well before the second runs out.

I got the cordless one over the corded cause I hate dealing with the cord and its also portable. But the corded one will have unlimited use (no battery, duh) and will have more power to keep cutting even when resistance gets pretty high.

As for dremeling different materials, you need the right cutting wheel (or grinding wheel, etc.) and the right speed. So make sure you do get one that has good speed adjustment. Mine has a wheel thing that I turn to choose speeds. It seems pretty smooth in its increments (which means its small increments) and has a supposed max speed of 35K RPM (not sure if that's true).

Btw, I have the 11.1V Lithium Ion Dremel.