What's the cheapest way to cube an item from Rare?

I've been having better luck with Plat cubes rather than regular S Cubes..

Since they've been out, I think i'm at around ~50 SCubes without any gears going from Unique-Legend, but when I used Platinum Cubes, all my gears got a tier up within 15 cubes or so, which I consider quite good (I've even had a few that changed tier in first 1-3 Cubes)

Also, while at Legend, I've been having good luck with them, cause I've been getting 18-27% stats relatively frequently of the % I want so... my experience tells me Platinums...

Then again.. it really is all luck each have their own preferred methodss

Your sample is way too small to draw any definite conclusions from though.
I have had such luck with S cubes before, and vice versa with Plats.
I think I will join the consensus and claim that while plats might have better percentage, it is not big enough to warrant the huge leap in price.