Can I choose whether hobbyist or Part 107 rules are more advantageous when flying a UAV for fun?
According to the FAA's own FAQ, you can do either (emphasis mine):


  There are two ways for recreational or hobby UAS fliers to operate in
  the National Airspace System in accordance with the law and/or FAA
  regulations. Each of the two options has specific requirements that
  the UAS operator must follow. The decision as to which option to
  follow is up to the individual operator. 
  
  Option #1. Fly in accordance with the Special Rule for Model Aircraft
  (Public Law 112-95 Section 336). Under this rule, operators must:
  
  [...]
  
  Option #2. Fly in accordance with the FAA's Small UAS Rule (Part 107).
  This requires operators to:
  
  [...]


So, it's your decision. But as always, ask yourself first how you would justify that decision to the FAA if something goes wrong. As a certificated pilot, you actually have something to lose if the FAA decides to take action against you.