How populated is Minecraft PC?

Well if you look at the statistics, minecraft has sold over 14.3 million copies on pc alone but has over 100 million registered users. It has also sold over 35 million copies across all platforms. But, almost half of all xbox players play minecraft on either trial or full version. Xbox has a total of about 82 million copies. So no, xbox has still sold more.

Since minecraft was released on PC first, is better on PC and is updated more and more often. Yes.

Much. Much more.-.

It depends on the server, but I'm sure there are both high-population and low-population servers on the PC.