So far as hybrid seeds are concerned it is a matter of knowing who the vendor is and their reputation. There are on-line sites where this question is discussed. Since I personally do not grow hybrids I can give only one recommendation and that because of my experience with their heirloom/OP seeds: Tomato Growers Supply. I am sure there are others whose seeds grow true to variety. So many seeds sellers outsource seed growing it is difficult to know where the seeds came from and from whom.
OP/heirloom seed suppliers tend to be smaller and more specialized. The big catalog sellers have recently been getting into the OP market but I stay away from those guys. So many have the reputation of sending out wrong varieties and often rename some of the old heirloom varieties to fit their purposes.
My personal favorites are Select Seeds, Tatiana's and Sand Hill Preservation. Remy, Tania and Glenn have wonderful reputations, excellent customer service and relatively low prices. In the last ten years I have not gotten a wrong variety from them in the hundred or so orders. Other sellers probably are just as good but these I give my highest ratings.
