I found the gen4 legacy more comfortable than my f11 5 series, but maybe that was because you had to stop more often to fill it up on long journeys....
To be fair my e61 was a long way from like a sofa. The m sport seats weren't great and the suspension was bumpy on anything but smooth motorway. Hence looking elsewhere. Though the comfort seats in the e61 (option extra) look plush.
I found the gen4 legacy more comfortable than my f11 5 series, but maybe that was because you had to stop more often to fill it up on long journeys....