I think that we have an interesting option available to us for the first time in years, now that Cesc is starting to truly shine and play near his potential. We essentially have THREE, not just TWO, fantastic midfield options that can be tactically manipulated in many ways depending on the scenario we face. I won't go as far as to say Cesc is playing on the level Xavi or Iniesta, but if nothing else he is hardly far behind as far as the current form of all three. (In fact in ways he is contributing more in certain areas than Xavi AND Iniesta, namely as far as assists/scoring/chance creating goes.)
Now, we have:
1. Xavi's - reliability; unparalleled ability to dictate tempo, control the game and retain possession; occasional creative forward pass; perfect central midfield positioning and ball distribution
2. Iniesta's - ability to maintain possession; keen eye for direct, attacking play; dribbling ability; large-game experience; assists and attacking intent; physical quickness, ability to penetrate via dribbling
3. Cesc's - scoring ability; near unmatched final ball; perfect attacking runs he makes into the box; decent possession skills; great lob passes and precise long-balls for even more directness
That is a very unfinished and rough list, but the point is that this dilemma is actually a great one to have. There will be times where a scenario calls for the Xavi+Iniesta combo, their strengths and weakness.... there will be times where Xavi+Cesc are needed and there will be times when Cesc+Iniesta is the best option.
I think these discussions of one over the other are somewhat pointless. Each have their strengths over the others and each are weaker than the others in areas. Finally Cesc isn't looking up to the others like he used to and is realizing that he is his own unique badass. Thus I think for the first time in a while we have 3 near equally good options at our disposal and that makes us a whole hell of a lot more versatile, for sure. I don't think its an either-or thing, just different tools needed for different jobs is all.
Xavi and Iniesta are already bonafied Barcelona midfield legends, I truly believe Cesc has it in him to eventually become one in his own right as well, maybe not quite at those heights, but truly great nonetheless.