Cheap. The expensive ones die twice as fast in my experience. Currently have a Westinghouse, after a Samsung died 2 weeks after the warranty expired. Have always paid $$ for Sharp, but the cheap Westinghouse is doing a great job.

I have a Samsung. It's small. 2 things it doesn't do is large popcorn bags and microwave rice standing up (I lay it on It's side. It does the job). Go with one that microwaves, grills and bakes.

Those flatbed ones where your food stays still seem interesting. They're a bit more than a traditional microwave but it could be worth it for the extra space