If only one choice - convection microwave, convection oven, regular micro, conventional oven? Can a convection microwave along with an induction cooktop effectively replace a microwave, conventional electrical oven and cooktop? I'm creating a small kitchen for a guest suite. One approach has a small electric oven with a cooktop and a separate microwave/exhaust system mounted above. Another thought is to forego the oven entirely and simply use a convection microwave for any baking purposes along with an electric (induction?) cooktop for cooking food that requires cooktop cooking. A convection microwave requires less space and costs less than an individual oven range and individual microwave/exhaust, though there is an additional cost for a cooktop. My concern is that baking/roasting/etc. in a convection microwave will yield less desirable results than using a conventional oven.
IMO only a good convection microwave can replace a normal oven. They're not cheap, but I often use mine rather than heat up the big oven for something small *. The heat is a bit too much from the top for some baking, such as tall cakes, but it's OK for most things and there are workarounds like preheating with a pizza stone or covering a cake with foil. 

I've actually got two convection microwaves (both Panasonic) because that's my main cooking option in the campervan when I've got electric hookup. I liked it so much I got one for home.

The biggest downside may be unfamiliarity - your guests may struggle to use the right combination of settings and accessories/dishes. They're also rather small so you won't be cooking a roast dinner in one. 



* combination mode is also very good for some things but take a little getting used to