What about "clean" vs. "dirty" loads in my pistols? What's the best to use? In my opinion, this is an over-stated "problem." In the purest view, obviously the cleanest load, be it factory or handload, is the best. In practicality, there's very little if any real problem. I've shot quite a bit of Sellier & Bellot ammunition in both 9mm and .45 ACP and the loads are dirty. The bigger problem a few years ago was their quality control as it was not unusual to get loaded ammunition with either no powder or obviously too little. This appears to have changed and the last batches I've tested in both calibers were pretty consistent in terms of velocity. In 9mm, the accuracy of the ammunition was also better. The stuff's still dirty, but it runs fine though my forty-five caliber and nine-millimeter handguns and I've seen it do the same in friends' guns. The same can be said for Remington's UMC and Federal's American Eagle bargain ammunition. None of these has caused malfunctions in any of my pistols due to their being "dirty" loads. Unless you're planning to shoot five or six hundred in a session in a lightly-lubed, very tightly-fitted pistol, I do not see any problems at all…and maybe none under those conditions.
I still use Unique for many handloads in several calibers. With most charges, this powder is not noted for cleanliness. I don't know how many thousands of 9mm rounds I've put down range using this powder and there have been exactly zero problems due to its being dirty. I'm told that the "new" Unique burns a bit cleaner, but I still have lots of the "old."
If cleaning is not a high priority for a shooter, I do think that a gun using dirty loads will begin to have problems sooner than if using the cleaner burning loads. If one routinely gives his pistols at least minimal cleaning and lubing after range sessions, I frankly do not expect that he'd have any problems due to his using dirty ammunition.
For what it's worth, the premium factory ammo intended for defensive use seems to be pretty clean stuff overall.