Neptune = 3.4/3.5TH and 2K at the wall per Tolip_wen
SP30 (Not looking at a late October batch) = ~4.5TH and 3k at the wall.

2x Neptune = 7TH and 4k at the wall
2x SP30 = ~9TH  and 6k at the wall.

Realistically for equal power to the wall you can run 10.5TH/s with Neptunes.

Right now the availability on both are close to the same (or you can buy someone elses pre-order).

I just find it funny that Roadstress sold over so many people (but gained "nothing" from it).  I know when the October batch of SP30s do it they will pick up the missing power, but since day one of your SP group buys you have trashed every single product.