I agree with Jerry.
For some very finely marbled briskets (think Kobe/Wagyu) I think very low temps are preferred. For Prime briskets, probably around the temps you mention, Brad. Butts, no, not if they're standard supermarket/mass-produced butts.
Can you do butts that low? Sure. Does it make them better? Not in my opinion.
I do butts much higher. Imo, butt does not need very low temps--the fat structure doesn't support the need. Yes, as Steve Petrone noted just today (in another thread) bark texture might be an issue at higher temps (or with higher temp spikes) but much of that comes down to personal taste, how finely (or not) the rub was ground, the contents of the rub (some things take higher heat better than others), and whether you rest the butt flipped (thereby increasing the potential for bark softening), or mop (ditto). I do not think butts are 'better' cooked at higher temps--I think they are pretty much the same--controlling for potential bark issues (again, according to preference) is all that is needed.
For pastured pork (not feedlotted, not mass-produced) things can be different. Finely striated fat and connective tissue (like one finds in Kobe) can be found in some of the pig breeds and in these cases a lower temp can be helpful. The fat/tissue structure is different--it often looks like less but is actually more (more renderable at the very least)--and lower temps allow more time for gentle rendering. With 'normal' butts the structure, though appearing like more, is less renderable (as compared to many heritage breeds) even though it appears substantial. It is substantial, it's just that it's not of the prolific/fine structure and treating it as such (by using low temps) can dry the meat if cook time is extended.
The trick with cooking tough meats of any variety and by whatever method--barbecue or braise--is to get a good sense of moisture content and fat/connective tissue content of the cut and select heat and time accordingly. Though nearly any tough meat of any internal structure can be cooked at very low temps, care must be taken to ensure tenderness without drying--which is a timing issue. Since hard and semi-hard fats are not going to render at low temps no matter how long the meat cooks excessive time is not beneficial for these (often mass-market) cuts.