My impressions using WSM with no water pan:
Reason here was chasing pit barrel cooker flavor (drippings to hit coals, burning fat creates desireable flavor).
Used a stick of applewood as barrier to bank coals. For cooking i used a chunk of mesquite and chunk of Almond wood. Maintained 250 dome temp, rotating grate every half hour. No wrap. Lots of damper adjustments and high maintenance. Sauced both sides last 20 min. Pic 3 is post sauced.
I really liked the texture of the bark. There was a crunch, like an unwrapped pork butt. Reminds me of backyard rib done over a weber kettle, by an unattentive and drunk uncle, but much better. Myself at fault here, but doneness was kind of a mess, crunchy bark but fat not rendered as much as i normally nail on WSM with waterpan. Doesnt taste like it was delicately cooked.
Very flavorful. I wouldnt have guessed it was a sauced rib while eating it. I didnt get any "grill" flavor by not using a water pan, but it was competing with a lot of flavors. I still think if grilled flavor were there, i didnt pick it up. I think the real difference here was texture, which was a neutral to negative to me vs. With a waterpan. I liked the crust, but the fat render wasnt as good. It was done at 4.5 hrs, so i dont think they got done in any kind of more expedient way than with a water pan. Maybe a rest wouldve helped.
Different, not bad, but not better IMO.
A PSA here, but Mesquite on pork is awesome. On WSM i only use one chunk, but i really love flavor.