Last gen every multiplat games got much more reviews on Xbox compare to PS3.  This gen, so far, it's all the way around: games are reviewed mainly on PS4. What can we learn fron that?

its only because there are fewer exclusives on ps4.

I don't get it.  Why having less exclusives makes more multiplat reviews on the platform?

Maybe it's just because the PS4 was released before the X1.

For the launch titles it's pretty obvious. The PS4 versions were the first ones released so they were the versions being reviewed. The ps4 should continue getting more reviews for every multiplatform that has a higher resolution on the ps4 though.

Surely this is because the PS4 is out in more countries....no?

PS4 versions are mostly superior that's why. Last gen it was the opposite.

Microsoft had embargoes on XBone reviews until almost launch day, whereas PS4 versions of the reviews were able to be published weeks before, so that contributed.