The best one is the one (or ones) that make you happy. There is a wide selection to choose from, so you should eventually discover what is best for you. If you are just starting out, and have no clue... Kalas, Ohanas, Mainland, and Fleas/Fluke are a great starting point. There are others too, but I can say from my own experience I have been happy with these brands. If you can visit a local uke group or music store, you might get to try out a few different models and sizes.
–Lori