I would determine which will give you the highest GH/s.
Well, that's .42 BTC if I invest into cex which is around 9.54GH/s, if I go with the antminers thats 6.4GH/s and 8GH/s if they're overclocked.
I'm just wondering if its more beneficial to have the antminers in-hand or the additional speed from cex.