What great bitcoin wisdom advice here....'Better play roulette' 'I advise you to play at a casino'

OP, if you buy any cloud mining contract and sit back and do nothing you are unlikely to come away happy. If you have the time to educate yourself a bit about what you are getting into then perhaps you can profit or at least learn something. With CEX and GHS you are buying a trade-able asset with a very liquid market, which also happens to generate dividends in the shape of mining returns once you have bought them.
GHS pricing has been downwards for months pretty much inverse to difficulty increasing, however that relationship has disconnected for the past 6 weeks or so as GHS pricing (in its market has found a bottom area and remained above that and slightly trending upwards).

thresher says CEX was the first one of 3 he pulled out of due to high costs on 'their shit scam site' but what he didn't tell you is that his PB money is completely gone as it can never be 'pulled out' and with Havelock the liquidity is so low good luck getting that out at a price you'd like.

Again educate yourself a bit about what it is you are buying into and the reasons for doing it and make sure you have an exit strategy as well as an entry.