I would never question the chops of Indy (or Miami). Both great teams. But you only have to play them a few times. In the West, you have to play OKC, and then San Antonio, and then the Clippers, and then the Warriors, and then the Rockets and then the Blazers, and then the Suns, and then the Mavericks, and then the Grizzlies. And then you start again... it never ends.
Otherwise, you are wrong when you say that "defense in the West is systemically lousier than in the East." The defensive efficiency stats say that Indy is the best defense by far, but after that, the top teams are evenly split between East and West. Meanwhile the offensive efficiency of the West is overwhelmingly superior - only Miami from the East cracks the top 8, and only three teams from the East crack the top 14.
And I would not "much much" rather play Indy than OKC. OKC is terrifying, top 5 in both offense and defense, and they will only be better when Westbrook returns.