Stupid question: How are these lightsabers different from the ones you build at the shop next to Space Mountain?
Not a stupid question at all!
First, Savi's is an experience in and of itself -- 20 minutes long, wherein a fully-in-character CM leads you through it in like a mystical Jedi kind of thing where you select your elements and the kyber crystal color you want (a little bit like "the wand chooses the wizard," iykwim), assemble it, feel the Force, light them up for the first time in a dimmed room with other would-be Jedi, all that stuff -- really really neat if you are into Star Wars (and probably even if you're not, but who's spending $210 on a thing like this if they're not Really Into It, lol).
Second, according to my SW-fiend son, "The ones from Savi's have metal hilts that are way better, their batteries are better and last longer, the blade is better quality
[it's plastic but looks like glass and my GOSH does the light look awesome!], it's balanced and has the right heft for like swinging around, and it's cool that which color crystal you pick also changes the sounds it makes. But the ones from the StarTours gift shop are cool too and way less expensive if you just want a decent lightsaber."
(He has watched a LOT of
youtube videos about lightsabers -- heft, lol)