I also have both the spiral saw(rotozip etc) and the oscillating saw. There is a time and place for both. In this case I prefer the rotozip due to mine having a vacuum attachment for dust collection, easier to precisely control the depth of cut, and the oversized foot makes tracing a straight line around a guide board very easy. In my opinion, the board trace method for long, narrow channels is the most professional. It gives a clean, straight channel, minimal risk of hitting something underneath, protects the removed sheetrock while off the wall, makes the final patch job easier due to the straight lines, and the patch screws being underneath the tape seams.