I'm a top elite member of all 3 alliances and I actually like them all. They all have their strong and weak points, but thanks to competition, they all have many similarities.
Sometimes a particular remote destination can dictate which alliance you use. But mostly I fly whichever one is the most convenient, or has a sale, or, lastly, which one I need the EQM's on to requal.
As for Oneworld, they have some great lounges and as an Emerald member you can use the F lounge in most places. They also have more flat seats in business class.