This isn't any help but it got me thinking - I think this is a mac/PC culture difference. You know when you build or buy a PC, there are a bizillion options to choose from, and so pages with massive tables of benchmarks for every conceivable model and variation of graphic card are very handy and look cool. One of the main passtimes of serious PC gamers when they aren't seriously PC gaming is comparing techniques to squeeze out extra performance.
But for a long time in the land of Apple, every one knew the graphics hardware was terrible, and so no one wanted to talk about it much. The last thing anyone wanted to see was a table comparing Mac framerates with PC graphics cards.
And now, even though Apple has some medium range medium grade cards in its hardware, there still isn't a lot of variation - you get to choose from what, 3 or 4 possible graphics configs in the iMac line? So no one is really falling over themselves to do grandular performance comparisons.
I think that's part of the background reason why such posts get a lot of "Sure, it'll work" or "Yeah, it'll run fine" sorts of answers. Mac users historically haven't needed to get a lot more specific (unless they wanted to embarass themselves around PC users).