technically just going by feats, what has the 9 tomoe rennigan actually done? well kaguya seems to use it to travel dimensions, and maybe to absorb jutsu. sasuke on the other hand, although his seems to be 6 tomoe as it has only had 9 tomoe that one time but i'll let it go here, uses his to teleport himself or other objects within a certain radius. that's about it. on the other hand you have the double rennigan which has many techs. it has shinra tensie, bansho tenin, chibaku tensie, limbo, absorbing, soul snatching, animal realm, renni tensie, the other healing tech, the machine parts tech and some other minor ones along with controlling the gedo mazo and using paths of pain. right now i like double rennigan better.