Bob, the big thing about a plug cutter is being able to match the wood and the grain in the plug. When you screw stuff together, if you plug with a dowel, the grain will almost always be at right-angles to the direction you want, i.e. running into the surface rather than along it.
You might make a feature of that, for example by having raised plugs, but generally you want the fixings to disappear as much as possible. So using your own plug cutter, you can go for the best match (to the grain) you can find in the scrap you're cutting the plug from. and if you get it right in three dimensions, you can shave the end down so it's really almost invisible.
I find them most useful with something like a 2"x1" piece of scrap: perforate it lots, on both sides, with the plug cutter, then a couple of releasing rip cuts with the bandsaw. That gives me a bagful of plugs, and I can experiment to find good matches.
The only awkward bit is remembering that the outside end of the plug is the bit from inside the scrap piece it's cut from, close to the releasing bandsaw cut. So you can guess, but not actually see the grain that will be revealed until the plugs are loose, and the grain on the outsie of the scrap piece is only a rough guide to how the plugs will end up.
If you get the sort of cutter that makes a conical plug (four blades usually), remember to go deep enough. If I bottom my nominally 10mm cutter, the point where the plug is 10mm is about 8-9mm from the narrow end. you need a decent amount in the wood to get a good fixing for the plug. The wider end you trim off, obviously.
And those four-prong ones only really work with parallel faced stock in a pillar drill. I don't have any of the other type, but I believe they can be used in a hand-held drill.
Have a go - even with a cheap cutter (mine are all really cheap ones!), you should be pleasantly surprised.
E.
