to some degree, especially wrt to moisture on the outside of food helping smoke particle to adhere long enough to be absorbed into the meat. The main difference I would anticipate is that having higher humidity in the air due to a water pan would slow down evaporative cooling of the meat, while simply spritzing would mean the air in the cooking chamber would be drier which would cause more evaporation and more cooling of the meat. So your spritzing would likely evaporate sooner (how much?) and cause a little more cooling (how much?) which combined with constantly opening to spritz would likely lengthen cook times.
However, if your trying to get more smoke absorption perhaps that could even help?
In favor of a water pan:
IMO, when I use no water I have to cut the vents down a lot, which means choking the fire more.
From amazingribs
http://amazingribs.com/tips_and_technique/zen_of_wood.html
"In the sweet spot of about 650 to 750°F, the best aromatic compounds for cooking come off, among them guaiacol and syringol"
Numbers I have read in other sources as well, such as Aaron Franklin's book. Secondary combustion of wood (a standing flame) occurs ~700
Perhaps this is where people often like stick burners more, and why methods like the snake and minion are more popular.
As Meathead points out:
"Build a small hot fire. You want to see flame. Fires burning in the 650 to 750°F range in the hot spots burn off the impurities that can be created in an incomplete secondary combustion. That means that you need a lot of oxygen so you want your exhaust vent open all the way. The hot air rising through the chimney will draw in air through the intake vent. You will probably want it open wide or close to it. Low smoldering wood creates dirty smoke."
I have definitely noticed on my 14.5 at least, that it is difficult to get enough air in, while keeping cooking temperatures down and not having to choke the coal's air. You want a smaller fire, near bursting into flames rather than a big pile of smoldering coal.
Having a water pan can help suck energy out of the air to lower its temperature while allowing more complete combustion of your coals, at least according to theory... so I have gone back to using it.