Currently, it is quite obvious that the Wii U is without a doubt better endowed than any current generation console. These anonymous sources do not contest the countless other sources that contradict such statements. They do not contest the quantitative information about the Wii U's abilities either. The possibility that the Wii U is not as powerful as current generation consoles is not what Nintendo fans or even objective observers are arguing against. It is a matter of its inconsistency with what we already know. Currently, and probably indefinitely, it is quite obvious these statements are paradoxical with what we know about the Wii U.
In regards to the other arguments involving the price of the console, it is illogical to think a controller, rather than a single entity within itself, will be substantially more expensive to produce and sell for "a" profit with a reasonable price-range. The hardware of the Wii U doesn't seem exceptionally new nor expensive, and from what we can tell from Nintendo's past, they tend to make the best use of the cheapest technology possible to maximize a profit. Furthermore, it is illogical to believe the competitors will be much different. As third parties target more and more consoles with their games, essentially increasing the ratio of multiplatform to exclusive games, so will companies worry less about the objective value and power of their console. They'll choose other, more preferential ways to make their console, and therefore their version of the games, unique. This is especially since development costs have not been able to viably keep up with hardware advancements.
On the other side of this argument, Nintendo will not choose to make a substantially weak console and miss out on these third party investments. That is one mistake they did not foresee with the Wii and I am sure they have learned from it.
In the end the overwhelming majority of information we have seen points in one direction. The Wii U is a generation leap in terms of concrete advancements. It might not be as much of a leap as the more powerful consoles of the 6th to 7th generations, but it seems agreeable among the credible gaming industry that it is a significantly, albeit not excessively, more powerful console than the current generation. Furthermore, the competitors will not be as distinct in terms of concrete power in relation to the Wii U. They'll maintain an affordability they hadn't targetted during the 7th generation. In the end, we will see something along the lines of the 6th generation in power differences. The only argument I can see left is whether or not the Wii U vs Ps4 vs Nextbox will be more of a Dreamcast vs Gamecube/Xbox in ability or a PS2 vs Gamecube/Xbox in terms of ability. That is a matter of specifics.