I would prefer one dog... but we have two, because in our situation it is the right thing to do.
We got our puppy (Dante) before when our Border Collie started aging, because an existing (good) dog can help train a puppy.
Then the Border Collie passed away, and Dante was noticeably depressed. Like crazy depressed.
So we started looking for an older rescue dog so Dante could have a dog.
We got Steve and Dante is happy again.
But Dante is obviously a dog's dog, he likes dogs to play with, and if he didn't, we wouldn't have brought in Steve.
Cons
90 lb dogs eat a lot
They make twice the mess
Twice the attention/time
Twice the vet bills
Pros
they play together and entertain each other
different personalities which is nice (Dante is PLAY! Steve is LOVE!)