Isn't he rated to be the better than Depay as well?
Not even close
So how good is he?
Well, to my mind Memphis Depay, who is 4 years younger, is already a better player and has the potential to become Van Persie/Robben level. Wijnaldum on the other hand is what I would classify as a fairly solid squad player at international level for Holland. For me, he probably wouldn't have been a starter in Brazil, and I think he was often the weak link when he played. Probably a similar level to Cabaye and Sissoko for me.
Sissoko with more technical ability/a brain?
Yes, if you want, and a little bit less strength and pace on the break.
From what I've seen Wijnaldum seems better off the ball than Sissoko, more intelligent runs.