you should be looking to use a compnay that can do more than just sell you the chemicals.
Every product line has items that REALLY work and others that fall short.
That's really all customers care about; price vs quality. If you nail that, with whatever product/method, you'll get tons of repeat customers.
These days especially, I stick to what works best for me and buy in as big a quantity as I can to get a per-unit price break.