Stratfor looks at the India-China rivalry.
And like I noted, discusses that the lack of a land frontier capable of supporting decisive ground operations limits their rivalry. Each in theory can push naval power into the other's backyard. And air operations can support their navies or operate across the forbidding land frontier. But the lack of ground options that directly threaten the survival of the other is a brake on competition spinning out of control.
Of course, once both sides have enough nuclear missiles to obliterate each other, the lack of a ground option becomes less relevant to the rivalry. And may make the political rivalry for allied allegiance in the region more intense.
From our point of view, just having two giants facing each other helps us keep one power from dominating Asia. We don't really need to ally with India even if domestic Indian politics would allow it. As long as it doesn't escalate to war, we're good. And as long as it doesn't escalate to nuclear war, we'll be okay. But a democracy will always be a sentimental favorite for us over even a shadow of communism government.