4K Gains And 1080p Parity
Now that we've seen all the individual tests, let's have a look at the aggregate results. Keep in mind that these results don't reflect the Mantle code path for Thief because there is no way to record detailed frame rate data while using that API. Remember that the Radeon R9 290X 4GB was set to the same clock rates as the factory-overclocked Sapphire Vapor-X R9 290X in order to highlight the difference between 4GB and 8GB of onboard memory. Also note that EVGA's GeForce GTX 970 is factory overclocked as well, to keep the comparison meaningful.
Let's first consider Sapphire's Vapor-X R9 290X 8GB vs. the Radeon R9 290X 4GB card. Performance is nearly identical at 1080p, but when the resolution is raised to 3840x2160 (4K), the Sapphire option gains a 14% performance increase. Compared to a stock-clocked Radeon R9 290X 4GB card, the difference would be even more impressive. In general I tell graphics card buyers that the amount of RAM is overrated as a graphics card attribute, and that's still true. But if you plan on playing games at triple-monitor or 4K resolutions, 8GB of onboard graphics memory becomes far more compelling. Based on this comparison alone, Sapphire's Vapor-X R9 290X 8GB card looks like a good idea for high-resolution duty.
However, we also have to weigh the GeForce GTX 970 option. While it's true that the EVGA Superclocked sample we tested for this article has a much higher core overclock compared to the Sapphire (115 MHz vs 30 MHz, respectively), factory-overclocked GeForce 970 cards tend to have higher GPU clock rates on average compared to their Radeon counterparts. Despite this, Sapphire's Vapor-X 8GB card did best the GeForce, on average, at 4K. But the margin isn't as impressive. At 1080p, where the GPU boost helps the most, the Radeon lost ground by a larger margin.
Of course, the key factor we haven't talked about yet is the price. Sapphire's MSRP for the Vapor-X R9 290X 8GB is $430. Compare that to a factory-overclocked 4GB Radeon R9 290X or GeForce GTX 970 in the $350 range, and the 8GB option is not as appealing as it could be. Sure, there's a decent amount of breathing room next to the $580 GeForce GTX 980. But unless you really need that extra RAM and can't live with the lower detail and texture settings you'll need to accept in order to play with a 4GB card at 4K, the cheaper options aren't bad. Note, too, that some of the games we tested don't even have options for true MSAA anymore, opting instead for processing-intensive FXAA.
On the other side of the coin, Sapphire's Vapor-X R9 290X 8GB is probably the best sub-$550 card you can buy for gaming on a 4K monitor. Another application we haven't touched on is GPU compute applications where a lot of RAM is required. Compared to a $1600 FirePro with 12GB, Sapphire's $430 8GB card looks like cost efficient option. Aside from these special-case scenarios, though, most gamers with a 2560x1440 or 1920x1080 monitor will be served just as well by a 4GB GeForce GTX 970. 4K monitor owners have more to think about.