meh.. I'd say try to listen to both in person. A lot of the character comes from the in-cabin noise. I like the BMW PE for the same reason that Dark_Knight_335 likes his Dinan. The only thing is I've never tried the Dinan.
I don't think that it's on all the time. Cold starts are loud, but it tones down to nothing after 45 seconds or so. I like that there is no drone at low revs, and the sound is a good balance between rasp and throaty at high RPMs (which I like). The best sound though, actually comes from the downshifts - can't beat it. Check it out - youtube vids don't do any justice.
'09 335i /i\ ZSP /|\ CA /i\ Piano Trim /|\ BMW PE /i\ AG M359