I don't think the only question is "who wins at having the most popular social network." The more concerning one is of exerting political influence through manipulative amplification/suppression (which is something the PRC has a lot of experience with). That could be both highly effective and extremely subtle and difficult to detect (e.g. activating one political tendency with relatively more call to action videos, while distracting its opposition with relatively more cat videos and relatively fewer calls to action).