I think you are comparing the minimum bandwith frequencies of both. CAT 6 is rated for min 250MHz and Max 500MHz and 6A for Min 500MHz and Max 600MHz. Does this make a big difference? CAT 6 can do 10Gbps upto 50Meters while CAT 6A upto 100Meters. I would surely go for 6A given a 20-30% premium...