I personally like Scrypt.cc alot.
I have tried both cex and scrypt.cc and made a bit of money on daytrading on Cex, but if you are interested in mining income I would definitely recommend scrypt.
The fees at Cex are pretty high, but I guess there would be alot of profit if you can afford to buy alot of GHs.
I am more of a smalltimer so I can easily justify rolling with a few khs in comparison to dumping my life savings on GHs.