We have used WD for a few years with ZERO failures and the three companies we buy hardware from use WD. If one of those vendors moved to Seagate, we would probably not purchase from them or buy diskless units for a while until we were satisfied they were just as reliable. Switching technologies is always a little scary, and I am sure that's why you're asking this question today. No matter how confident you are in moving, if you have a few more failures than normal, it may not be worth saving 10%. My advice, reach out to your top 20% clients and ask them what they think. Only do that if you're planning on passing some savings along or if you're just not going to increase the cost of your product do to other expenses increasing. I realize including customers in every decision isn't possible, but IMO something as crucial as HDDs warrants a little more effort on the manufactures part.
Our best vendors and the people I want to buy from, reach out to us regularly for our opinion. If it goes south (sometimes it does) I don't mind because they warned me.
BTW, Seagate should be doing better than 10%. If whoever is negotiating this deal for you can only get 10%, you need to buy them "Secrets of Power Negotiating for Salespeople" and require them to read it before their next meeting.