What do you have time for? Kittens and cats alike are pretty self-sufficient all around and even if you do work 8 hours a day, you can get a kitten with no problems. Just shut doors to rooms you don't want him going into and keep plenty of toys around. Chances are, he'll sleep when you're gone and perk right up when you come home. But kittens need a lot of play time, so if you choose a kitten, be prepared for that. You also need to make sure you're well equipped for the "kitty teens." When the kitten turns about 6-7 months old, they will act up and be nightmares without a firm hand and training. This is when they like to push boundaries and get into a lot of trouble. You also need to consider that all the shots and getting it fixed is YOUR responsibility, if it's needed.
The benefit of having an older cat is that he's already established and will be calmer.