That is a tough question to answer. There are pros and cons to each..
Getting a puppy?
PRO: You generally have a clean slate and an eager learner. If you start training immediately and are consistent in your training, there is high likelyhood of having a well-adjusted adult dog. You are in control of how the puppy experiences the world.
CON: Yes, you have an eager learner but that puppy needs to learn everything from you over the course of a year or more. Consider potty training; which can take weeks or even months of getting up in the middle of the night to let the puppy out. You also have to puppy proof your home. Training and socialization are exceptionally important and must be practiced daily.
Getting an adult dog?
PRO: Many times you have a dog that has learned all the basic commands, is potty trained and has already learned that chewing on shoes is a no-no.
CON: You many times have no idea what life experiences that dog had as a puppy in the form of socialization and training. From this, many adult dogs can come with emotional baggage because previous owners were not knowledgeable about raising a puppy. I call rescued adult dogs “project dogs” for this reason. As a trainer, all the rescued adult dogs that I have seen need some kind of training or rehabilitation.
The conclusion is, have an argument with yourself weighing benefits and pitfalls of adopting either a dog or a puppy. It is always a good idea to enlist the help of a qualified trainer to make sure you start your relationship with your dog or puppy on the right footing.