Depends on which country you are in. In Australia some years ago Rena air pumps were the best but most were single outlet. They were a bit pricey but good quality and lasted decades, with only the diaphragms and flutter valves needing replacement occasionally.
There's too many brands out there to say which is best these days. Go to a pet shop and ask them to let you hear each air pump they sell. Some pumps are quieter and some are noisy. Have the pump run and pump air through an airstone in 18 inches of water. If it is quiet when doing that, and it produces lots of air bubbles, then grab it and get a couple of spare diaphragm and flutter valves.
If the pump is quiet when not connected to the air stone but becomes noisy when pumping air into the water, it is not a good pump.