They are both pretty much the same in my opinion. I hauled US Mail for 25 years for a company that had a contract with the USPS (United States Postal Service). They would bid or renew the contracts every 4 years. We pretty much kept all the bids or runs. Just be on time and don't be an ***hole to the postal personnel and you keep your contract. Their were O/O contract drivers too. I am actually going to work for a contractor that hauls for UPS and FedEx. The bad thing about being an O/O you get the less desirable routes that the bigger companies don't want to bid as low as some O/Os are willing to pull it for. I was going to get my own truck and get a mail route. But all that is usually left over are crappy routes that don't make enough profit to mess with. Don't let me discourage you. Sometimes you can get a decent route that's left over. Like I said, this is the postal service that Im talking about. UPS could be totally different.