I don't like butting outside corners because no matter how good the joint is, sooner or later it will show up through the paint. I also don't like the looks of flat sides on cabinets and use fiinished panel sides instead. What I do is make up plenty of lock edge mitered stock with extra for the exposed outside corners.
The end panels are in addition to the interior sides ofl the cabs, and are left loose on the back to they can be shimmed tight to adjacent window or door casings.
I rabbet cabinet bottoms and insert into dados on the sides with the rabbeted edge up. Straight dados are too hard to get tight on the visable side because of the thickness variations in plywood.
If the plywood is just a little thick, it will put a kink in the side when it is inserted. If it is a little thin, the joint doesn't look good unless you shim it to the top side of the dado from the bottom. Neither of these conditions exist if you rabbet the bottoms.
If I were required to make flat, flush exposed cabinet ends, I would miter without the lock edge.
Last edited by clampman; 02-04-2008 at 10:56 AM.