there are lots of factors to be considered, what you love doing the most that's the most important factor for me , cause an engineer who isn't passionate about what he does, will quit or half ass his job, cause engineering is crazy hard, for example Adrian Newey is the chief engineer for red bull f1 racing, he spends months working on the car engineering new parts and what not , and even when they are on a plane back from a race, he still has his old sketch book , that's someone who loves his jobs, and that's what makes the difference, every genius idea he makes in the pinnacle of motor racing finds it's way to road cars, same goes for other amazing f1 engineeris , think ABS, Traction Control, Drag Reduction, Kers, seamless gear change, carbon fiber, floppy pedals all these were invented by F1 engineers, they don't get paid say like bio tech engineers but they make their mark,
I my self I'm in the field of software engineering, I love doing it cause I love artificial intelligence and I find it fascinating which will help me withstand the crazy hours, I put looking at weird algorithms :p or insolvable problems
now if money is what makes you tick here are few links , keep in mind what's the sect, that's an other money factor
link link