PS4 is selling faster than the PS3 by a significant margin and less product shortage issues. Though those are ultimately the biggest factor in most early sales.
XB1 sales do seem lower, and that is because the PS4 is seen by so many people as categorically better. The PS3/xbox one, still to this day it's hard to physically compare them, one was more difficult to code for and they have different cpu's/gpus. This generation you can compare them almost directly and while Xbox tries the "edram is sooo good" route most people go 1.2tlfops vs 1.84tflops.... errm, win?
I wouldn't be surprised if Xb 1 numbers are down after the first couple months, PS4 doesn't appear to be and is selling great. Handheld devices have been selling well but moving ahead most people are going to opt for and stick with smartphones for convenience, cost and relatively close levels in performance.
Wii U, tanking, Wii sales had been tanking for quite a while as the fad wore off. A huge portion of people who had a 360/ps3 will get a new gen console while I think fraction of people who had a Wii will buy a Wii U. I mean, Ps4 has outsold the Wii U already, ouch.
The "console" market might in fact shrink, but so what, that doesn't mean the PS4 will make any less money, nor the games released on it, nor the ones made for the X1.
In terms of performance, meh, the only possibility for this gen was SOC's, that was a monumental disadvantage in terms of how much they could fit on a single die, so the performance they got on an integrated die is huge. Likewise tflops console to desktop can't be directly compared. Even with low level API like Mantle, the APi's on consoles are lower and have unified memory which is worth another chunk of performance. I'd say it's closer to double the performance. but the last gen consoles were superseded by the 2900xt/8800 in short note and had half the effective performance as they do now anyway.
The highest end gpu's at the time the consoles came out didn't use 250W, it's a completely different market on desktop gpu's where 300W became the limit since the last consoles launched.
The consoles launched with effectively the same power as the 120-150W cards of the time, and have roughly speaking done so this gen. It happens that at the time a 120W card was a x1900xtx, highest end of the gen and the consoles were around that power level(but with improved architecture and low level API).