What's better to say, "Come va" or "Come sta"?

I always say "Come sta." There is probably nothing wrong with saying "Come va," but it seems more informal and I would rather stay with the formal with adults that I do not know. With children, I usually say "Come stai."

Come va is translated loosely as "How's it going", while Come sta is more "how are you doing" (slightly more literally, "how do you stay").
Come va or come sta are the formal uses used when you don't someone very well, for elders, people who are above you in society (bosses, etc).
Come vai or come stai would be appropriate for your peers. I used the informal often when asking questions to people who looked about my age or less and nobody complained. :)

Ray,

Based on the my Italian language training, the more polite greeting would be Come Sta. The phrase Come Va tends to be a bit more "informal".

I try to avoid using Come Stai as my Instructor indicated this is used only by very close friends or family. In some cases, even people that have known each other for a long time still use the polite form of the greeting.

I believe these conventions are similar to use of Tu or Vous in French.

Cheers!

I would never use "come va?" with someone I do not know well.