A prosperous China is my preference, maybe today PRC and India don't enjoy the level of diplomatic collaboration compared to India and US, and have a tilt toward Pakistan, but Political diplomacy is not always a permanent policy in International politics, things change with time. US allied with Pakistan before PRC did, but we can see things are gradually changing. A strong PRC being a neighbor with all issues with India solved will be a good indicator for the development of Asian continent compared to US trying to influence from the other side of the world. Being a neighbor I believe PRC and India will share some common strategic interest and the idea of peaceful co-existence in the near future with PRC tilt towards India, if PRC need to project herself as superpower she must act reasonably in her domain and neighborhood to make a world influence rather then letting a rival knocking at her door step.
Regarding the authoritian administration that PRC exercise upon her people, I believe it is something to be left upon the people of China to decide, if they feels it ok then its their call, but if people revolt against the system their is a whole army of pro-democratic nations around the world to support the cause.
Development of PRC will directly or indirectly have a positive effect on India while the well being of the US might not be so.
leaving aside military ambitions India and PRC share many common voice in the UN against the west, (like economic forums and environment issue). If the fucking problem of border issues could be solved with PRC and Pakistan just think how much Asia can develop and put on a checkmate for western policies and dominance. SCO could be a good initiative for that.
Maybe the world as a whole won't be benefited from such a development but my belief is that the region will for sure, after all some one need to loose for someone else to gain.
N.B. I am not a pro-PRCian, my views just exhibits my vision of the future development of India and Asian at large.