For two dogs, you will want to order two leashes and one belt. For instance, you could order a Runner's Choice with a belt and a Runner's Choice without a belt.
When it comes to deciding which leash to use, we can tell you that most of our customers who do this buy two of the Runner's Choice leashes. Part of the reason is because two dogs side by side often end up in front of the runner. We also had customers buy one Runner's Choice and one SideKick. This combination is good if you have two dogs that want to run on one side of you, or one dog in front and one to your side.
If you decide to give this a try, know that you can always exchange a leash if the initial combination is not right.