Here we go again - you'll never actually answer questions, will you? You just try to throw them back with your usual arrogance. It won't work this time.
I'm still waiting for you to explain how W/gh/s does not equal J/GH.
So now 'you' challenge anyone to show that the SP31 is the best option. In case you've forgotten I've already challenged you to do a detailed comparison of the AM solution versus the SP30/31 (which, of course you're incapable of doing so because you don't know how), so either provide it or shut up. And don't cheat by 'overclocking' - a device has a specification, overclocking it means going above that specification so there is no guarantee it'll work properly.
Are you incapable of doing anything yourself? In case the answer is no, I've changed the 2 numbers on the calculator for you:
SP31
AM tubeIn the case of SP31, anyway the ROI will be better if these machines can be delivered early October; Being alone with a huge hashrate, and a low cost hardware, gives a very fast ROI.But, we are not in this case anymore. And the ROI stage may take months, or can't never be achieves if new machines with a better J/GH and a better price are there in the months to come. The risk is mainly related to the future hardware designs.