You're not smart if you GCU, Amazon Prime or PUR Pro.
They are only worth as much as your likelyhood to use them, and having multiple in concern is very likely to make the value of all of them lesser.
Unless you do your own math and know your own habits, it's not particularly smart to have any of them.
Plus, I'm not exactly thrilled with Gamestop right now. They themselves haven't come forward to customers informing them of their data breach over the Christmas season. Now they screw up this?
Yeah, that's exactly the sort of company I want holding some of my personal information.
Different memberships have different benefits, and companies have their own prices and deals throughout the year.
Amazon Prime is hard to compare because most people had it for the free 2 day shipping, so they don't feel like they're paying extra for a membership to get the preorder discount. That being said, purely comparing it in terms of gaming deals, it's not as good as GCU since it doesn't apply to used games and doesn't have the points system nor the occasional coupons either.
GCU is probably the best in terms of what you get for the reasons explained above, but you're paying purely for the gaming discounts rather than having as an added benefit to the 2 day shipping, which sometimes doesn't feel as good of a value if you don't buy a lot of games.
I hate Gamestop, but they do have some good deals on used games (especially the older games) a couple of times a year, so you might save a decent amount if you like buying a lot of used games that were released a while ago.
Unless you only buy like 2 games a year, no one is "not smart" for having any of those memberships. The savings quickly add up, and for Amazon Prime the savings on games is not even really the main point of the membership.