In 1947 and 1949, they were in very similar conditions.

Not true. India was in a much better state well into the 70s, inheriting a lot of the British built infrastructures, and was able to trade with both the East and the West. Whereas China was completely war torn, and for a time, isolated.

Even though the PRC was proclaimed in 1949, the CPC at the time only controlled half the nation. Fighting with KMT and its aligned warlords on the mainland continued until the mid 50s, with smaller pockets holding out for several more years after. And not long after that, the Sino-Soviet split happened, compounded with the already placed US led sanctions, China was basically cut off from the rest of the world for nearly two decades. The fact the CPC was able to turn their fortune around and become an emerging super power is an amazing feat.

India more or less squandered its head start with its incompetent government, and it has only gotten worse post 90s with it fully embracing neoliberalism and religious fanaticism.

A Red India, would probably have seen the bigger picture and accepted Zhou Enlai’s border agreement, preventing future conflicts, and China would have been able to skirt the economic and technological sanctions via India, saving some hardships of the 60s and 70s.

Both nations would be more prosperous today, perhaps even tipping the scale a bit, preventing the Soviet collapse.