My vote goes to #2.
I have two rescues, and while I adopted them when they were younger (2-years-old and 8-months-old), an adult dog can fit into a new household incredibly well. This past summer I had a Yorkie X foster who was anywhere from 3 - 9-years-old, probably around 7-8, and she fit in wonderfully. You just can't explain the feeling you get when you're lying there with a dog curled up beside you...and you know that you saved that dog's life and gave it a chance that it never had before.
Of course, if he's not what you want and you won't be completely happy, then it might not be the best decision. I had to look for a long time when I was adopting a second dog to find just the dog I was looking for and I couldn't be happier
.
Whatever you decide, good luck!!!