He did both for years. What did he get in return? Piccolo, Raditz, Saiyans, Androids and Cell. This was Goku experimenting and trying to see if this would work and it did.
He did it train? What is your proof to back it up? You do realize the entire other world arc is filler right? Not canon in the least.
Nah, he trained in other world in the manga too, they even showed South Kai. The Other World training was how he learned Super Saiyan 3, and how he found out about fusion.
However, the training was just a perk. Goku wouldn't have stayed dead if he didn't think it was the right decision. And then all throughout the Buu saga (until Toriyama just went and dropped the whole plot thread
) he was trying to find a successor because he didn't want everybody relying on him all the time. He was dead, a relic of the past pretty much, so it was important the Earth had its own people to take care of business.
Goku's basically the athlete/traveling musician pops. His kids don't hate him cuz even though he ain't always around they know he's out there living his dream
