It depends on what type of campaign you want to run. Smuggler, Bounty Hunter - Han Solo pre-ANH style stuff is Edge of the Empire. Wedge Antilles, Storm Trooper, etc is Age of Rebellion. Force powers is Force and Destiny. All 3 are compatible - for example, my party currently has 2 Force sensitives, 1 bounty hunter and 2 rebel soldiers. We all work for the rebels so our campaign is based on AoR but we each use our own "thing" (Morality, Obligation) on top of the Rebel duty system.
Not legally.
I touched on it in 1 but basically the mechanical rules are 99% the same. Big difference is Obligation vs Duty vs Morality. Morality for a force user in particular plays a part in how your character develops skills (more than duty or Obligation in my opinion) since some force powers require you to fit in a certain morality threshold so we have a split system where we use our own systems ability on top of the Duty system for the AoR campaign. So my player, being a force wielder, has both a morality score and a duty score. They are tracked separately and I gain or lose points in both seperately.
This RPG is more narrative than the DnD system. I find it nice to have a map for combat or encounters where it's hard to keep track of things, but you won't hear people saying things like "I move 5 feet to the right to get a view of Vader" - just makes it easier to visualize what you are doing.
To touch up a bit more on the differences - just because you buy AoR first doesn't mean you can't have force powers - they have rules for it, it's just more limited and the gear isn't all there for different saber hilts and crystals. Likewise, you won't find as much on ship to ship combat in F&D since that isn't really the type of campaign a force wielder would use. It's still there for when you need it but less detail and equipment for it compared to AoR. All 3 are very fun. Also you asked earlier about playing the Empire in an AoR campaign - that's possible in the book but harder to design a story for, and IDK if that book has any starter empire stories in it (my GM has the book at his place or I'd check).