you're in MD, not Fl or some other southern state, so I need to ask.........Is this "sun room" a 3 season room........or a year round room with heat and AC?
Often they may look pretty, but get extremely hot in summer (even with ceiling fans)..
Not quite sure what you mean by "will be added to all 3 levels" (do you mean it's a 3 story addition?), also don't know what [rice range you're in....but........
my immediate response between the 2 options is......go with the finished basement.
Families with children appreciate the added play space or space for optional home/office or even potential au pair suite.... more