Both of these on a 1920x1080 monitor. Which one will pull ahead..specifically in a hardcore raiding scenario (25-man)? With the i5-2500k processor, if that matters at all.
If you're looking at simply WoW then they'll be very similar. However, it's very likely at that resolution, future games will make better use of the 2gigs plus you can just overclock the one to get some performance boost, with the VRAM you're screwed if you happen to need more.
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VRAM does not equal video card speed. The higher the resolution is the more VRAM you'll use, also depending on the game's texture load. The main reason for getting a card with higher VRAM is supporting larger resolutions/multiple monitors and/or games with higher requirements (like Crysis 2's hi-res textures)
At 1920x1080 both cards should have roughly the same performance... but the 2GB version might have better longevity depending on how much VRAM games start using in the future.
This and the post you quoted are a little misleading. Having more VRAM on a graphics card is going to result in a very minor increase in performance for games that aren't going to require full use of the 1GB. If a game, and there are quite a few out there now, requires more VRAM due to high textures and high resolutions games may run slower or in some cases as pointed out earlier won't run at all at those higher settings.
Gamers with a 1080p monitor need to try to look and purchase at least a 1.5gb VRAM card if they're looking for keeping it around for some time.