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.
The way people earn money with cex is by trading mining shares, just like trading altcoins. Would you hire out your mining power with a loss? Neither will cex.