I'm certain this has been discussed at length but I can't find a "search" function so:
I've been running My Macbook Pro 15" ( 16G ram, 2.5g I7, mid 2014) on El Capitain with no obvious issues. Shall I upgrade to Sierra? Advantages? Problems?
Sierra is the next step from El Capitan in the evolution of macOS... your MacBook will run it quite well and requires no more effort than El Capitan. Go for it... and High Sierra should not be an issue, either.