And you can read Mike calling Jens the best person he's ever worked with in various places.
OK, this point is a wash. Flip a coin.
What, the 5.1 mix of Stupid Dream is subpar now?
HARDLY! I could've picked any of PT's 5.1 releases, and the point would be just as valid, IA just happens to be my personal favorite. And the guy's stereo mixes of these two records, for example, are also production masterpieces that I can't imagine anyone else improving. Don't get me wrong, I think Jens is also great, and would hardly be disappointed in hearing him get the nod, I just happen to prefer SW's style.
The only reason I'd care if it was Jens or Steven doing the album would be for the 5.1 mix. For the CD version of the next album, it really falls down to Mike how it sounds, and the CD version is the most important thing the band has to consider.
5.1 is a nice bonus to have, though, and Steven is definitely better than Jens at that.
Either of these guys would do a great job with either the stereo or the 5.1 mixes, it's really splitting hairs and personal preference as to who you'd prefer to do it.
Seeing the progression from Morningrise, to My Arms Your Hearse, to Still Life, I don't have any doubt at all that Opeth could've produced Blackwater Park in all its glory without Steven Wilson. The band was clearly improving dramatically with every new album in those days. And look at Opeth without Wilson - Ghost Reveries and Watershed sound even better than your Opeth trinity... at least to me.
The vocals would've changed, however.
I'm sure they could've done a great job, just not
as good, IMO. As for the "progression", the musical approaches in both songwriting and overall sound have changed greatly since BWP, speculation on whether or not the last two releases would or wouldn't have sounded better with SW at the helm are just that, speculation. Steven's own chops have improved and "progressed" over the same period as well, as have Mike's as a songwriter and an ever-more confident producer in his own right. Again, it's all personal preference, but I think you'd have to admit that both guys would do a great job. Hell, I'm not so sure that the
real best man for the job might not just be Mike himself at this point!