Who can tell me which is better
Well which is “better” is your prefernce. The California has slightly angled rims. The dv888 has flat rims. The california is tall and skinny, the Dv888 is shorter and wide. The both have large gaps (Dv888s larger) and the same FundaMetal quality feel. Because the California is bigger and lighter, it should be fast and a tiny bit floaty. The Dv888 has a good pace, not fast not slow. The choice is yours.
Um, which one has better performance, and which one will sleep longer?
About the same. And for spin time, they would both spin the same. Spin time varies from person to person too. Either way, its all about what shape do you want, because on performance and spin levels, they are the same.
would a konkave bearing help cuz i have one
ive never thrown a california but the dv888 is one of my favorite all time yoyos behind the boss
konkaves wont make it better
it just prevents it from hitting the sides. Anyway neither of them is better, all yoyos are good. It’s just that the Cal2010 has butterfly wingshape and the Dv888 is flat rimmed. I suggest you the Cal2010 because it has the same shape as the X-con
both are good the only difference really is shape i personally like the DV 888 
Then again, I doubt you’ve even tried the California.
Since you seem to be more like a beginner to metals, just get whichever looks cooler to you. You will most likely like either one of them, so it’s okay to just go for it. 
Samad I’m sure you’ve played with a lot of yoyos in your day, does the Cal2010 play like the VK bc they’re made by the same guy, and which one is it more similar to, VK, Dark Magic (not comparing smoothness of metal), or 888x
The vk is a small bearing california.
Not nessiserily, because this is the 2010 version, and the sizes are different, also the VK is bead blasted, but I’ve never played with the California, and also the 2010 version has no hubstacks, and if you say is true, the new version is said to be a lot smoother
So which is more smooth, 888x or 2010 California
Samad is somewhat correct i haven’t tried a Cal but from my friends they said there wasent much of a difference
i havent played the california but i highly, highly suggest the dv888 it is SUPER smooth and it feels and playes awesome, you probally cant go wrong with the california but the dv88 AMAZING.
calafornia 100%
the California. but the dv888 is still good and it has good smooth throws
also california 100%
which one makes you feel what you want
but anyway california