Wasnt the Jag s'posed to be the 'ultimate' bass at the time, a higher quality bass? I would guess then that the wood would be better selected.....
As to Jap re-issues, you are caught in the trap of 'best available at the time'.....
All MIJs are very nicley made, however a good J re-issue could well be, nicer than a Jag re-issue.....
Not much help, I'm afriad.....