I wired my garage in EMT with surface-mounted metal boxes mounted to plywood. I'll try to post up some pics tomorrow.
I am struggling with the same question right now on the new garage I am about to build (21'x45') I see three advantages to the approach and one downside as compared to Romex under the drywall.
1. I am really confident in the EMT installation. I hang all kinds of things up with screws or nails into the plywood. No chance of accidentally hitting wires.
2. It's really easy to modify. I have made a few changes and added some outlets over the years, including a 100A 220 circuit for my phase converter. If you go this route, leave poly lines in place for fishing wires.
3. The biggest: you don't need to figure out where everything goes in advance.
The thing I don't like about it is that it interferes with placing cabinets on the walls and storing things up high.
I'm positive I'll want to change things after I put in the electrical. I'm looking at 3 options:
1. Run Romex for the 120 and light 240 stuff and plan on running EMT for the welder, the 3 phase, and the filtered power outlets,
2. run surface mount EMT over plywood, or
3. run EMT on the studs and use furring strips to hang the gyp board and plywood so that the outlets are flush.
If I go with option 1, I will run 12-3 Romex to the outlets with both phases, so I can wire for 240 or 120. I plan on adding a crazy number of boxes.
I welcome feedback as well.
Best,
Bob