I bucket it into there being three options: genuine, clone, and good-clone.
We had a bad run with fs.com QSFP+s. Their SFP+s have been better to me, but reckon I have had a couple fail.
Atgbics SFP+s have been a reliable clone supplier for us. I don't think I have had any of those fail, and they have been my main vendor for a while now. You can order them programmed with personalities for Cisco, etc.
Part of the edge of fs.com is that it is so easy to place an order and get fast delivery. My main site is in another country to where I live, and I do a few trips a year. Several times they have made low-notice projects possible.