1. Obito never said that.Obito states that, RSM Clone's Chakra wasn't enough but 100 Healings Seal's was.
Plus weren't we discussing whether Sasuke'd be more useful than Sakura? Since on panel, we see Sakura be of some use.
2. You brought that latter part up on your own. The OP asked how things would turn out differently (not 'would Sasuke be useful') and my post was centered on how it wouldn't turn out any different if it happened in the same way as canon not that Sasuke would be useful.