Logistics, not a ranking
Buying metal through a screen is identity of the dealer, payment, shipping, and what happens if a parcel never arrives. This page is a watch-for list. It does not rank vendors.
What to watch
Who they are: a name, a place, a history you can check without their own FAQ. How you pay: some methods are cheap and reverse; some are final. How they ship: insured, signature, discreet, and to an address you control. What the invoice says: product, weight, fineness, serials if any, and the premium you actually paid.
If they will only “store it for you” and never ship, you have the storage problem in another costume. If the price is an outlier, you have the fakes problem in another costume.