It changes all the time. Depends on the current price/diff which there are sites that track that for you.
So my question is which site has the most accurate price/diff
www.whattomine.com keeps track of a few algorithms and exchanges. It's a good place to start.
Good place to start. But there is no end all be all answer. You need to constantly be looking at the markets anticipate markets, etc. But what you might want to look for is a multipool that mines the most profitable coin for you and charge a fee. Might be the easiest way for you.
What multipool do you suggest?
