I've worked a lot of different jobs in a lot of different industries. Honestly, I haven't found any of them particularly easy or difficult. Having to deal with the public as a cashier at McDonalds has a different type of "difficulty" than flipping burgers, which has a different type of difficulty than working in a manufacturing plant, which has a different type of difficulty than being a manager or a pencil pusher.
Just this week I was talking to a young attorney who was telling me how easy his job is, he does initial consultations for a large law firm, gets paid nearly $100k just to talk to people - and he admitted that most of the time they could get the same advice for free just by using google.
I'd imagine that being a brain surgeon is pretty easy, for trained brain surgeons. Just the same way that being a rock start is easy for rock stars, and being a professional golfer is easy for professional golfers. Once you know how to do something and are skilled in it, then everything is easy.
Someone who had only been in my industry a few months asked me if it ever got easier. I told them no, it never get's easier, you just get better at it.
I'm really not sure that any particular job is more productive than another - they are all needed, and all are easy once you become skilled at that particular profession.