If you are talking manual transfer switches.....get a 200A one, and switch the whole dang panel! Then....you can use whatever you want. That is how my house is setup. It is outside, next to the meter. There is a conduit ran from the transfer switch to the shop, where I can plug my generator welder in. WORKS GREAT! You can use a smaller generator just to run lights/tv/etc. Then if your wife needs to cook, laundry/whatever....use a bigger one. That is what I do.
I can get a 200A manual service rated transfer switch for $500.00 last I checked. The best way to go! If your service is bigger....they make bigger switches also.
Or are you wanting a autostart up deal?