I don't know why you would want to use Druddigon in UU, since its official tier is RU. At least Dragalge is BL2, so can only be legitimately used in UU.
But neither one should really be used as a Sweeper. Sweepers by definition have high Speed and high Attack/Special Attack. While both Druddigon and Dragalge have a high Attack/Special Attack stat, both are very slow. (EDIT: Dragalge's Special Attack isn't that high, but its ability, Adaptability, gives it good power regardless)
Dragalage is a great Special Wall or a Tank, but definitely not a Sweeper. It has Adaptability, so its Draco Meteors and Sludge Waves do a ton of damage. It also gets good coverage moves like Thunderbolt or Scald.
Druddigon, on the other hand can also do some good damage, with Sheer Force and its high Attack stat, but it again its low Speed doesn't mean it can be a good Sweeper.
If you want a good UU Dragon type Sweeper, try scarfing Hydreigon, or using Dragon Dance Salamence or Haxorus. Neither Dragalge or Druddigon make good Sweepers, although both have other roles they do fill quite well.
If you insist on using one of them of as a Sweeper, then try Scarfing Druddigon, as it will probably do slightly better than Dragalge, thanks to its naturally higher Attack, and slightly higher Speed. Just don't expect it do that well.