Yes - there shouldn't be much difference.

A while back Pacific were offering bigger commissions to travel agents on Hanoi/Saigon. So although the official price was the same, some agents were offering a slightly better price by refunding back some of the commission.

Another point: agents usually charge extra for credit cards. When comparing prices you should be clear exactly how you intend to pay. If paying by credit card it can be cheaper to buy direct from the airline office as they don't charge extra for credit cards. Also quicker - many agents don't print tickets (which is why they sometimes offer to deliver for you!) but get them sent from the airline office by bike. Wastes a lot of time.