Try one, it is what your legs/knees think about it that counts, your brain should not be bothered with this..
Depending on what you need (hilly area? distance pr
day, your fitnes) you should care more about what gears you need, not how many they are. If you ride a three gear bike and do not like it then find out why you do not.
To explain it: I picked up a steptrough bike at the dumpster last sumer. Rode it for some weeks to decide if I liked it. It had a Nexus4 hub. Found I only used two out of four gears. The sprocket on the hub had 18 teeth. I tryed bigger ones and ended up with a 23 teeth sprocket. That gave me a good gear range for my riding in this area. Decided I had too many bikes and gave it to a friend, she like the bike a lot. I do not think she would like the bike if it had the 18 tooth sprocket still on when she got it, and also I think she would not have beenable to tell me why.
If you have many gears on your bike then WHAT gears is not so important, you can always find a gear to use. If few make sure they are the right ones.