Being uke on the street would certainly not help against an attacker; as they wouldn't be throwing you, they'd be striking. It would increase the time a fight takes and you'd be very tired at the end if you kept on trying to roll. It much be much easier and a lot less time to slam an opponent to the ground and pin them and be done with it.
As far as learning 'volumes' from nage by being uke, it wouldn't matter since you'd be uke for the rest of your life, you'd never use the knowledge.
So, I'd take the nage route.