Reputation, product quality, price, shipping time, customer service. In that order.
I'm new here. Not a bad board but a lot of people shilling for certain sources/products. It can be hard to tell who's not getting paid to hype up sources. I find evolutionary.org has a better review/comments section/system set up. A longer track history. A lot of the sources here are advertised on Eroids as well so I can tell this site is legit. Eroids is king tho. Before pulling the trigger on a source here, I'd research it a bit on eroids