They are both bad deals as far as I'm concerned. However if I had to chose I would say PETA is a better offering simply because they have track record (along with HW online now).
Here's a simple comparison:
PETAMINE: $3/gh , ~1w/gh, $0.25/kwh hosting
CBCM: $2.7/gh , ~1w/gh, $0.3/kwh hosting
Rockminer: $1.1/gh, ~1.2w/gh, probably less than $0.3/kwh wherever you live.
Just notice that Rockminer does not provide PSU with their product...you have to add that factor into calculation.
each RX-Box needs a 800W PSU, that is about $260(
BTC0.4). So Rockminer: $1.5/gh, ~1.2w/gh.
And Petamine is under their way to reduce the power consumption, to ~0.75w/gh.
So in the long turn, PETA hosting fee 0.75w/gh * $0.25/kWh= $0.0001875 /Gh
Rockminer in your home 1.2w/gh * $0.15/kWh= $0.00018 /Gh, plus you have to manage those miners yourself.
So far Rockminer only wins in $/gh, but there are numerous things for home miners to dealt with, $1.5/gh is way below the true cost.
Especially for those who want massive Ghs and don't want to build a datacenter themselves.