I agree with your conclusions about mining with cex.io and pbmining.com
I have accounts with both companies, and currently pbmining.com performs best.
It definitely has the lowest rates of 0.0064 BTC/Ghs for a 5 year contract, but you should not invest a huge amount.
pbmining.com
this is still market speculation, however you look at it, never pay out more than you can afford to lose.
CEX.IO offers now also Future Minning contracts which start 26th April 0.0081 BTC/Ghs (FHA) and 26th May 0.0041 BTC/Ghs.
This looks very atttactive to me and the rates are comparable with pbmining now, and you have the security of mining with the market leader in cloud mining.
CEX.IO
'the market leader in cloud mining' I will have to dispute, what they do is allow you to trade GH/s on ghash.io; being the biggest pool does not in any way make you the market leader, more rather - the easiest option for many.
It also gives you the flexibility to convert your Ghs back to Bitcoin after a month or so if you think it doesn´t pay off.
The trading platform is great, and its a lot of fun anyway. You can start with 0.5 BTC if you want or even less.
under your proclamation you should have the text;
^^advertisement^^yes, we know all about both these companies, hence why we were interested in the OP in the first place.
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just had a thought tho.. I suppose prices on cex are always fluctuating also, so stick with the original comparisons i think . 
