Hmm, he was probably just stressed out over the change, he'd get used to it after a while and like more space. But bettas do have different personalities, maybe he does like his origional home better. Or maybe something in the water was different.
You could try putting him in the new tank once he's better for a day, and see if he getts used to it (use a little aquarium salt?) and likes it. If not, then put him back to the home he likes.
Just an idea, but keeping him in the home he already likes would make him happy too. :)
Was the environment different, like the bigger tank had more water movement or sound than the smaller ones?