Let's assume Brown moves up in his prime and faces the pre-Hagler Mugabi. Who wins? No need for judges here, that's for sure.
I think you're right but this would probably been a good fight to bet on the underdog if the odds were really good.
Mugabi by KO, somewhere around round 5. It would be exciting for the first few rounds, but Mugabi's firepower eventually gets Brown out of there.