From personal experience, you may want to contact all the vendors you can to see who has the best deals, best reviews on this site, and make the decision from there. All the vendors here are legitimate and vetted as stated by
@PTFC and nobody has an issue with them for the most part. If you do encounter an issue, contact the vendor first and if there's any further problems that the vendor cannot resolve a moderator can assist you with your issues or provide advice on what to do.
Regarding the "best" vendors out there, it's all a matter of choice to be completely honest. I found one vendor to be better for me personally apposed from the rest, yet I know someone that prefers another vendor. It's all about preference. I'd say try out a few vendors, especially the Mexican vendors which you only need to donate $10 to obtain access to that section along with helping keeping the forums going. So you'd be killing two birds with one stone.
Always be informed by doing your research before ordering from a vendor. Go through all the recent posts regarding people that ordered from the vendor(s) at least a months worth of reviews before ordering. See if there's any issues, if there were any see if they were resolved. If they weren't you now know what could happen. There's always a risk of packages being detained by customs officers no matter what vendor you use however that rarely happens.
I hope this helped, stay safe and informed!
-VII