That sounds backwards. Generally the blue has 32mb cache and black has 64mb cache. Go to WD's web site and look up the model of those drives to verify the amount of cache. Gaming performance should be negligible due to the cache size, however, the blue most likely spins at 5400 rpm vs the black's 7200 rpm. The 7200 rpm drive will have better performance.
According to their website, all WD blue products have the same rpm (7200), but you're right about the cache size. An online retailer mentioned some weird specs on their HDD's which is what confused me.