This is all very interesting. Terry Williams was the drummer on the Brothers In Arms tour. And the setlist included Ride Across The River and Your Latest Trick. And we know that Terry was great at concerts, but not in the studio? But I understand the subtle differences:)
One of the best quotes I know is "Your band is as good as your drummer". A drummer and a bass player are the foundation everything else is built on top of, rhythm-section is the most important part of all this. I still remember working as a roadie on jazz festivals and listening to drummers and bass players essentially providing 80% of the experience on soundcheck. It's jazz, it's swing, it's the feel, drive, and emotion, it's everything.
The difference is very subtle, but not so much. Pete Best played with The Beatles for 2 years before being famously fired and swapped to Ringo Starr to record in the studio. Fortunately, we do have recordings with Pete, and it's quite obvious why they would do this, he just wasn't great, and the studio amplified it 1000 times. Even Ringo was replaced by a studio drummer to record "Love Me Do", and he felt that he would also be fired. But we all know how it went for him.
So never underestimate the importance of the drummer. Mark got EXTREMELY lucky having a drummer as good as Mr Withers and got equally unlucky with his departure, having to resort to changing drummers as gloves for the rest of his career. Now, don't get me wrong, Terry IS a great drummer and always has been, just maybe not suitable for every song out there, I think Mr Dorfsman explained it best.
For Mark's first solo album, should he still prefer to stick with Dire Straits, it would most certainly have John Illsley replaced as well because songs demanded the same versatility from bass as drums in Brothers In Arms and On Every Street. As we know, this is pretty much what happened anyway, and John Illsley was replaced with mighty Glenn Worth who can play any bass and any bass line in existence. And even with "One World", John was already replaced for 1 song.