Some dogs that are NOT neutered spray to mark their territory. So he may spray in your house when he gets older. Also, there is a high risk of unaltered dogs getting cancer. It's much safer to have dogs neutered/spayed to reduce this risk. I've also heard the unaltered dogs like to roam (to look for females).
My friend Brittany has a website which discusses spaying and neutering. It is
www.mylittlemia.com She is also a member of YT. She has a lot of other useful info on her website as well.
I have my both dogs altered and I'm so happy I did it. They are better behaved and I don't have to worry about them getting cancer at an early age. Good luck with your decision!