I guess you'd already need 50% more power to produce anything even remotely noticeable.
If you had 50% more RAM, 50% more clock in a PS3 or 360, it would be a huge difference vs the other. These are console that battle for 5%.
Or consider the uproar, if Sony disabled 200 MB of RAM (<50%) on the PS3 for some reason. Would that be "barely noticeable" too? We've fought this gen over a few MB's of RAM more that the PS3 OS takes than the X360. Or MS just rejiggered it's disk with a full update to gain 1GB more storage,
I read the report to mean under clocked, Wii U is barely more than PS360. If it was fully clocked, you would see 50%.