Good to learn all of it in my opinion. I hate sprinkler fitters personally... They whine more than sparkies. That said, the requirement for sprinklers guarantees wages and work, so there's that. Sprinkler fitters typically make more than plumbers from a paycheck standpoint. Plumbers make more as a small business.I'd suggested focusing more on the plumbing side, I've worked in construction for 30+ years. Focus on new construction and not repairs. It's his choice, however. I think there's a lot more work for sprinkler fitters than there used to be around here as the building code now requires them in all multi-family construction. I think anyone that has their red seal and wants to work will have lots of opportunity over the next 20 years or so as the current journeymen retire.