<Snipped quote by Double>
Unless you live in GT hell which is kinda cardboard.
GT is not canon. Well, okay it is canon... kind of. It's in its own little alternate timeline. That was the explanation for it (and the Movies) offered by Xenoverse 2 and that's what I'm sticking with, personally.
As far as the actual mainline Dragon Ball universe... death follows an odd set of rules, not helped by them being retconned later in the series run on top of that.
In the beginning of the series, no one was supposed to be allowed to keep their bodies when they died. That's why all the dead people you see were characterized by the little cloud things. They're just souls with no bodies. Goku kept his body because of Kami. When Goku died, his body faded out of existence, and Piccolo confirmed that as Kami's doing. Even when Goku was wished back after his training with King Kai, he still needed to meet with Kami at the check in station in order to be transported back into the world of the living.
Fast forward to the Buu Saga, when Vegeta was about to blow himself up in a last-ditch effort to kill Buu. He asked Piccolo if he would see Kakarot in the other world, and Piccolo says it's not likely. He tells Vegeta that only those who were good and died selflessly are allowed to keep their bodies in the other world, and all the evil and horrible things Vegeta had done throughout his life up to that point probably meant he would just be another faceless soul and sent to hell to boot.
So there ya have it. Death was a lot harder to come back from in the early parts of the series even with the Dragon Balls. But once Kami was written out and fused into Piccolo, they couldn't use him as the explanation for fighters keeping their bodies or being able to return to the world from the check in station. So the rules were retconned into the way Piccolo explained them in the Buu Saga.
No matter which set of rules we follow (Personally I prefer the earlier rules that require us to make use of Kami, if just to give the old guy something to do) there's a pretty slim chance that a murderous Android who hates all of humanity is going to be keeping his body in the Other World.
