One last note: I switched to antpool from slush, I dunno if this is a factor in it or not.
Its relatively normal, depending on which CGMiner version i'd use i'd get different hashrate too, but poolside, nearly no difference.
For pools, i'd recommend http://www.kano.is/index.php the payouts are much less steady but its less fee and better payouts into accounts of several factors, such as optimized pool code.
Thats the one i use but i think the most important point i'd like to advocate is pointing hashrate away from China. They centralized enough hashrate as it is already, imo.