I have a greenhouse just for my Orchids and C&S and some odds and ends, and it is part of the house. I love it!
You are in zone 8b, and as you said you will heat it.
So, personally, I would always prefer to have a greenhouse attached to the house, if somehow possible/there is room for it. It will be more energy-efficient, since you can circulate the heat from the house through the greenhouse and back. The greenhouse will heat your house on sunny Winter days. ( many times the oil burner here doesn't need to kick it until the sun goes down) And it is much easier to step into it during the Winter.
