Hold on there.
The Wii U in general is a more powerful console than the Playstation 3, it has more
RAM available (
2GB on the Wii U against just
256~512MB on the PS3) not to mention it has
a good advantage in GPU and overall speed as well from the internal memory.
You can clearly see this advantage in games like Need for Speed: Most Wanted where the Wii U version had higher quality textures or games like Call of Duty Black Ops 2 where the Wii U not only had better textures but also loaded with higher speed.
Not to mention that while many games were screen-tearing on the PS3, they were almost non-existent on the Wii U.
In addition to other games like Watch Dogs and Batman Arkham City in which the Wii U version had some more graphic details that were not present in the PS3 or X360 versions.
The only
big downside of the Wii U is that it has a
considerably slower CPU than the PS3 (it was the sacrifice made to maintain backward compatibility) this is the reason why many games have a very low frame-rate.
But overall, the
Wii U is indeed a more powerful console, not by much, but it is.
The PS3 could never run something like
Breath of the Wild for example (even more because it is one of the only Wii U games that uses more than 1 GB of RAM, it just has no RAM available on the PS3 to run something like that)