[JimD]

An electric grinder looks similar to the vibratory cutter but they work very differently. The grinder just spins a disk of either abrassive material or steel which has abrassive embedded in it. The disks I can find for a grinder are meant to cut metal or masonary. No disks meant to cut plastic. I'm sure they would cut it but they would make a relatively wide slot and would cut by a combination of rubbing the plastic away and melting it. You might distort the dash because of the heat and if there is a wire close behind the plastic you will go right through that too.

The vibratory cutter moves back and forth and has a cutter with little teeth in it like a saw. So it saws through material. If the material you are trying to cut moves with the blade, it does not get cut. If it is rigid it does. Wires should move and not get cut. Dash will stay put and get cut.

If you control your depth of cut with a grinder or something else you could avoid damaging wires or other structure under the opening. If you aren't careful you could make a big mess.

Jim