Hitting dragons is a pretty big deal, although I honestly have yet to use clear smog in a battle, I don't know though it may be just how I play. So I am actually thinking about sludge bomb > clear smog, also being about to insta-beat opposing blelooms is pretty cool, and on a side not sludge bomb poison hax could really help vs Jellicent, Sableye, and Mew.
Some other notes:
This thing has HP divisible by 8, which should mean that it should run only 248 HP to reduce rock damage, although I'm not sure how generator effects this.
I don't see why black sludge can't be used either, if your using this as your rotom counter, it shouldn't be a problem, trick all you want rotom.