Hi BadgersMom.
We have two beagle girls, litter sisters. I found that with our first (Bonnie) she was really needy and would cry when we got home and wouldn't settle until we picked her up and nursed her (just like a real baby). When we picked up the second from the breeder (Pearl), Bonnie was all of a sudden little miss independent. From our experience two is better than one. They do everything together, like two peas in a pod. We even have one dog bed that doesn't get used because they prefer to sleep on one bed together.
The good thing about having two is that they actually roll around play fighting for most of the day which wears them out. And being pack dogs I think they love the extra company when Hubby and I aren't around. But in saying that, they do sometimes do naughty things together as well.
And as JerryGov said, when one starts baying the other has to start and/or check it out too.
All in all, I really did notice how much better off Bonnie was when we bought Pearl home, but that could be because they are litter sisters.