I tried all 3 of the careers in the beginning. I liked the Dr. career best, so that is the one I pick whenever I play with GTW.
It gets hard at times to diagnose some patients, just go to the next one and then come back to the hard one.
The longer you play it, the staff becomes elders, then they die (some die on your shift), then they become ghosts who still work there. I don't care for this part. When they die, let them be gone. It gets to where all of your staff workers are ghost :(
It's a lot of fun, I even enjoyed the science and detective careers when I tried them out.