Big Law litigators IMO, don't get a good education being a litigator.
I think the key is to know what you want to do long term and then take the job that makes it easiest to get to (obvious I know). For AUSA, I assume you need to make connections with the AUSA office that you would want to work for, so I would get a job at firm in the market you want and make sure you get a lot of courtroom experience in that market.