8.75 durability for big block street/ Strip

I'll weigh the S60 when I pull it out. I'm replacing it with a 9 inch so I'll weigh them both to see if there is any difference. The S60 has a Detroit Locker in it so it is heavier than a spool. The 9 inch will have a S Trac in it and it will have a Pro series cast iron center so it isn't going to be a lightweight. I expect the 9 inch to be roughly the same weight as the S60, might be a few lbs lighter.
Simple question then, ....why? To get rid of the locker in favor of the gear limited slip?