I started flying (16) before I started diving (18) and found the experience made me a much better diver on several levels.
I think pilots in general are a bit more comfortable with procedures and with mechanical equipment in general and this trasfers directly to diving. In my case finishing, owing and maintaining an experimental aircraft took my mechanical competence to a new level.
They are also attuned to thinking three dimensionally and have a much better grasp on navigational concepts like terrain navigation, compass headings, reciprocal bearings, etc.
I also think that instrument rated pilots have an advantage. I don't think this stems so much from a "know how to trust the instruments" standpoint (although I don't know many non instrument rated divers who can hold course and depth mid-water at night for any significant distance). I think the primary benefits are the concept of flying with total precision that is gained with an instrument ticket and also from mastering the task loading that is required to be a competent instrument pilot.
I have found this to be particulary beneficial on deep/technical dives. In my experience once you master the basics, most instrument instructors pour the task loading on you mercilessly (and then induce some vertigo) to force you to speed up your scan, adapt and prioritize to manage a situation. This tends to reinforce the need to develop your planning and organizational skills to enable you to stay well ahead of the aircraft even in rapidly changing situations. The skills developed there easily exceed what is demanded of you in terms of planning, organization, and task loading even on deep technical dives where you may be under the influence of narcosis.