puzzle: who wins?

Who wins in this position:....

 Edit: The pawn was on g7 in the original, but it is now moved to g6.

...and why is this position different from the position below:

The first position white immediately checkmates with p=Q. The second position White still wins but in a different manner. g7 and next move p=Q either wins the rook or checkmates.

Interesting!

I think that kind of puzzle is essential to improve. Thank you for bringing it.

Gabriel

I made a mistake in the first position... now show why they are different.