Now, on all of my answers on questions like this, LETZ COMPARE DEM!!!
D-Man aka Darmanitan:
The reason I call this guy D-Man, is because he is D-Man! He makes one of the greatest sweepers, to be honest, ever! With that amazing 140 base attack, plus the 95 base speed, he is capable of launching some extremely powerful hits, with devastating effects. He can relate to pokemon like Rhypherior, who have 3 great stats, and 3 not so good ones. His defence, special attack and special defence are very low, so you would have to be careful while using him as a sweeper and he doesn't K.O.
The Fire type of the three elemental monkeys. Compared to Darmanitan, his stats are well rounded. But that can also be his biggest downfall. He will easily be OHKO'd by the simplest of water type moves. However, this thing packs a punch with Nasty Plot, and as that being one of Smogon's best sets for it, he definitely makes a great sweeper. My only worry is that he could be taken out before he even starts sweeping. Same for Darmanitan.
Both good fire types, but I would go for Simisear. He may not have as much attack or overall power as Darmanitan, but he can provide good sweeping too, with more speed, and access to special and physical moves he can use effectively. For all out power though, D-Man is your man.