Welcome to the forum. Have you driven a Crossfire yet? I would think that would be the best way to compare the seating of the 2 cars. I have never driven a Z3, so I couldn't tell you, but I know I am in my mid 50's and the Crossfire isn't the easiest car to get out of, but driving it makes that small inconvenience worthwhile.
Good luck with your search, that are some good deals out there.