If the difficulty will be just a bit better than in your projections then the SP31 is clearly a winner. I can't help noticing that after the so praised ROI the S3 is doing close to nothing, while the SP31 is still doing something. Also I can lower the power efficiency down to 0.58W/GH and doing that will help me earn more money after difficulty reaches 70 billion so getting ROI will be faster than in your projection.
You are forgetting to add in the hosting costs $400/month
Not even in Advania I'm not paying $400/month. My October SP31 will be hosted with jtoomim where I will pay ~$240/month.
Could you post a link to jtoomim website, please?
I'd like to find out more info