Last night showed that Iniesta still has an intelligence and movement about his play that makes our players more "involved". IMO that's better than Xavi who completed around 130 passes or so yet really didn't provide anything. He wasn't even controlling the game for us, nor playing the best options, and often strayed forward for some reason without attacking. Iniesta is pretty much a CM nowadays, he does more defensive work than Xavi and drives our play more even if he doesn't have the same glorified and padded passing stats.
IMO that's why Cesc-Iniesta is our best central midfield. Both players provide their own skills, complement each other well and make up for any deficiencies the other has, and are productive/creative. Cesc gives us much needed penetration and fluidity in creating chances to finish and he can linkup well. Iniesta provides his trademark weaving movement around and really facilitates the play to keep things running.