We've answered the architectural efficiency question. Now let's look at raw value, in terms of price and performance.
Even though we're using a geometric mean to average performance across the five games we tested, the Radeons' unusually poor performance in Arkham Origins has an outsized impact on their overall 99th percentile FPS. I think an adjustment may be in order, so I've provided a separate 99th percentile scatter plot with the Arkham Origins results removed from the calculation.
In my view, the outcome here is pretty straightforward. Nvidia is apparently rather proud of Maxwell, and it has priced the GeForce GTX 750 Ti accordingly. The 750 Ti offers lower overall performance than the card it replaces at $149, the GeForce GTX 650 Ti Boost, and it's also slower than the Radeon R7 265. Since Nvidia has killed off the 650 Ti Boost, the Radeon R7 265 captures the value title at $149. If you base your buying decision solely on price and performance, then the Radeon is the card to choose.
But the GTX 750 Ti can go places the R7 265 can't. The reference GTX 750 Ti is 5.75" long, doesn't need an auxiliary power input, and adds no more than 60W to a system's cooling load. The R7 265 is over eight inches long, requires a six-pin power input, and draws up to 150W of juice, which it then converts into heat. For many folks choosing between these two products, those factors may matter more than the difference in performance, especially since the GTX 750 Ti can provide a very nice gaming experience at 1080p. You've gotta think the GTX 750 Ti will be the animating force behind a legion of Steam boxes.
The Radeon R7 260X and the GeForce GTX 750 offer nearly identical performance at $119, but many of the same dynamics apply otherwise. The GTX 750 requires less power and doesn't need a six-pin aux input, for example. Also, in this case, the difference in noise levels is huge. The reference R7 260X registers 47 dBA on our sound level meter, while every GM107-based card we've tested flirts with the ~32 dBA noise floor in Damage Labs. I'd call this an unqualified win for Nvidia, except that the R7 260X has 2GB of memory, twice what the GTX 750 does. That fact didn't seem to harm the GTX 750 in our testing, but the Radeon is arguably more future-proof. Let's call this one a qualified win for Nvidia and add an asterisk about the memory size.
In the larger picture, Maxwell's arrival signals a big change in the GPU space for the coming year. The only way AMD managed to maintain a good position on our value scatter plot with the R7 265 is by offering a much larger chip, with double the memory interface width and more than twice the power budget, for the same price as some fairly lightweight hardware from the competition. That's what happens when you lose the technology lead, as AMD has learned rather painfully in the CPU market in recent years. My expectation is that Nvidia will roll out a whole family of Maxwell-based products in the coming months. Those are likely to be much faster and more efficient than current Kepler-based cards. I'm not sure what AMD can do to answer other than drop prices. Heck, I don't think we know much of anything about the future Radeon roadmap. AMD seemingly just finished a refresh with the R7 and R9 series. Looks like they're going to need something more than another rehash of GCN in order to stay competitive in 2014.
Thank goodness I'm forced to be concise on Twitter.