I dont think Agency matters - what matters to me is the instructor. You will learn a whole lot more from an instructor that dives and has a background in the diving you want to do - lots of different environments, various conditions and conditions you are most likely to dive in. If you are a cold weather diver - don’t bother getting your AOW in the tropics - imo...
Ask the instructor questions on what you will learn and how it will apply to the diving you think you are more likely to do. Ask them how long and what types of diving they do... Who was a recent student and can you talk with them?
Remember you are paying them - check them out like you would a priced item you are buying - do some research...