Graphics card hierarchy
Quick hierarchy chart
This chart shows the approximate performance hierarchy of current (and some past) graphics card models. Keep in mind that (factory or user) overclocks on these cards can put them ahead of their nearest upper neighbor and can sometimes even put them ahead of several of their upper neighbors.
Before making any purchasing decisions you should always check reliable benchmarks of the graphics card you are considering. It's also important to note that the hierarchy order depends on what specific game or benchmarking program it is being tested with, so it is advisable to look at the benchmarks for the games you are going to be playing, and the resolution and detail settings you want to play these games at.
More video memory on a videocard won't make it faster in all cases, it will only make a videocard faster for specific games that use a lot of video memory. Certain newer games can take up a lot of videomemory and so can "texture mods" for games (modifications from enthusiasts that add more graphical detail to certain games). Lastly, using very high resolution or very high filtering settings (AA for example) can cause a game to use more video memory. Using multiple monitors for gaming can also be a reason for wanting more video memory on your graphics card but it's important to note that this is far from the only reason. If you can get a videocard with more video memory available for a reasonable price difference it's probably a good idea to do so.
The cards marked with * are dual GPU videocards. Dual GPU videocards balance the load over 2 GPUs in exactly the same way a CrossfireX or SLI setup does. Due to the nature of CrossfireX and SLI it depends a great deal on the specific game you are playing whether performance will be much higher than a single GPU card. Because of this, the dual GPU cards can often be several place below where they are listed in this hierarchy. They won't often be much higher than where they are listed though. Keep this in mind and read up on how these cards perform for the games, settings and screen resolution you want to play at!
|Graphics card series||Remarks|
|Both are dual GPU cards and are often to close to call a clear winner in performance. The HD 6990 has 2GB of effective videomemory, even though it has 4GB in total. The GTX 590 has 1.5GB of effective videomemory, even though it has 3GB in total. This is because each GPU has it's own dedicated videomemory that cannot be shared with the other GPU.|
|HD 6870 X2*||Dual GPU HD 6870 card with 1GB effective videomemory, even though it has 2GB in total.|
|HD 7970||AMD next generation GCN architecture, AMD 7xxx flagship single GPU card.|
|HD 7950||AMD next generation GCN architecture.|
|HD 5970*||Dual GPU card with 1GB effective videomemory, even though it has 2GB in total.|
|GTX 580||NVidia 5xx series flagship single GPU card.|
|HD 6970||AMD 6xxx series flagship single GPU card.|
|GTX 570||NVidia 5xx series (lower) high-end card. Close to the HD6970 in performance but with only 1.25GB standard memory complement vs standard 2GB on the HD6970.|
|GTX 560 Ti 448 Core||This is not the normal GTX 560 Ti! The 448 Core version has the same GPU as the GTX 570 and GTX 580, the same memory bus width as the GTX 570 but fewer streamprocessors than the GTX 570 and GTX 580. It's really a slightly cut-down version of the GTX 570 rather than a family member of the GTX 560 series. Unlike the GTX 570 though it does not allow for 3-way SLI setups.|
|GTX 480||NVidia's flagship 4xx series single GPU card.|
|HD 6950||AMD's popular (upper) midrange offering|
|GTX 560 Ti||NVidia's popular (upper) mid-range offering.|
|HD 5870||AMD 5xxx series flagship single GPU card.|
|HD 6870||AMD midrange.|
|GTX 560||NVidia midrange.|
|GTX 470||NVidia (lower) high-end 4xx series.|
|HD 6850||AMD (lower) midrange.|
|GTX 460 1GB||NVidia midrange 4xx series card.|
|GTX 460 SE||Scaled down version of the GTX 460 1GB which also has 1GB memory but only 288 shader processors compared to 336 on the normal GTX 460. It also has a lower stock clock frequency of 650MHz vs 675MHz on the normal GTX 460 1GB.|
|GTX 460 768MB||A lower memory version of the more mainstream GTX 460 1GB which as a consequence of the lower memory also has a smaller memory bus width of 192 bits vs the normal 256 bit bus on the GTX 460 1GB making it's memory bandwidth lower on top of the lower available memory.|
|GTX 550 Ti|