It all depends on your game. Both companies are regarded as among the best in the sport and I love paddles from both. They are reliable and made with cutting-edge technology.
While Selkirk once had a reputation as being better for power, JOOLA's new paddles are right up there. I'd recommend searching my pickleball gear reviews for specific Selkirk and JOOLA paddles. You can also take my pickleball paddle quiz.