Lanai is very isolated. If you want seclusion and beauty, this is the place. The beach next to the FS Manele Bay is great -- one of the best body surfing beaches in Hawaii, IMO. I've never stepped foot on the other FS on Lanai, but I'd imagine it's even more isolated.

Maui has more restaurants and activities, and it's also beautiful.

Personally, if I lived on Maui, I'd want to go somewhere new.