I put my toaster oven in the cabinet under the stove top and put it on the counter when I'm using it. It is rather a space hog, but I don't use it all the time so that's okay. I don't see any reason to have a microwave on top of that. I figure if I need to reheat anything it can go in a pan on the stove or in the toaster oven. Gee, kind of what was done before microwaves became so popular!
The cabinet where the microwave is usually located (when installed by ETI) is where I now stash my collection of cat-themed kitchen towels, my tote bag of things for when I'm driving and my purse (which ain't small; yes, it has cats on it). And whatever else I decide to wad in there while camping. It holds lots of stuff!