Kain_Highwind, certainly one test will not prove that, so I probably should have added"in my opinion" to my post. From my tests and Meow!s, I would say it is better unless you are facing CH120, but this is just my opinion for now. I'll try to watch out for that in the future.
Ultra(and everyone else), I have done Duo SP230 D tests and it isn't that good as I saw from my informal testing, but I apologize for not posting real tests first. My theory is that since Phantom has more
pure stamina than Duo, and is mainly blocked from contact by SP230's disk, it is basically a battle of pure stamina, which Phantom is best in. Duo, which is better while making contact with its opponent's metal wheel, is usually blocked, putting it at a disadvantage against Phantom. There is a small chance it could be the weight of my Duo and Phantom, but I doubt it.
MF-F Duo Aquario SP230 D vs Phantom Gasher B
Duo:2 Wins(All OS)
Phantom:18 Wins(All OS)
For anyone interested, I have also uploaded a video showing SP230's stamina on Phantom and D.
http://m.youtube.com/watch?v=gVWYfTStEtI