They have more room in general especially rear leg room so more comfortable long journeys, longer wheelbase helps with this and ride quality.
You can carry some pretty long objects in an E38 iL's too.
Sure they don't handle as good as 3 and 5 series but they actually are surprising decent, they just a heavier 5 series at the end of the day. I took mine to the track and had certainly more fun in it, probably more than i would have had with a 318i auto or similar