First of all, material. You can choose between wood, aluminium or carbon fibre. Wooden paddles are usually aesthetically very appealing, with beautiful varnishes showcasing the wood grain. However, they tend to be heavy and more complicated to maintain.
Aluminium paddles have a huge advantage: price. On the other hand, they still are heavier than carbon fibre, and more dangerous for the rails of our boards and our feet.
Finally, carbon fibre paddles remain the most appropriate for sup. They are lightweight, strong, sometimes adjustable, yield great performance, etc. The only negative side is price, but think of it as a long-term investment.
Adjustable or non-adjustable paddle?
Purists will tell you that a good paddle can be used for surfing, riding and racing. If you want details, know that as a sup neophyte, an adjustable paddle will allow you to find what size suits you best. An adjustable paddle can also be used by the whole family. Inevitably, though, adjustable versions are heavier and less rigid than a non-adjustable paddle.