The compressor, of course, is key; if you are balanced precariously on the edge of buying a big(ger) compressor, then the air tools make sense; no air, no air tools. Jeff and I have been debating this (electric vs. air grinders) for some time now - I like the cable driven electric 1/4" and 1/8" pencil grinders; Jeff likes the pneumatic versions. Unsurprisingly, Jeff has a big compressor, and I have a small one. If I was choosing exclusively between the CHEAP versions of each tool - and I had the air - I'd get the air versions, imagining they would last relatively longer than the electric versions.