If you have an Amazon Prime membership, it's almost always cheaper to pre-order from Amazon. In addition to the other Prime perks (mainly free 2-day shipping and Prime Video), you get a 20% discount on new games, which means you will pay about $48 instead of $60. This applies to pre-orders and purchases of new games within 2 weeks of release.
PlayStation Plus can get you great discounts, but they vary from week to week. PS+ almost never gives you a significant discount, if any, on new AAA releases. A few months after release, you might get a smoking deal from the PlayStation Store, with an extra discount for being a Plus member. I would not expect a major discount on FIFA or WWE for a few months after release, at best.
That said, you will still need PS+ to play online multiplayer, so unless you want to just play with a buddy on the couch (which I like best personally), you will need to ante up for it anyway.
N.B. The price of a PS+ membership is increasing from $50 to $60 a year in September, so if you can afford it buy it now and save yourself $10. It doesn't appear that Sony is offering anything new for the extra money, so I'd rather see you keep that ten spot than line Sony's pockets.