I'm a big girl with a Great Dane (Jax) so I got the Xlarge Buddy System.  I've only had it a week but so far it's working really well. Jax walks great on this, right beside me without pulling and it's saving my poor arm. It's also really nice to have your hands free. He is 7 months old and weighs 112 lbs right now so I will update when he gets larger and let you know if he's jerked me off my feet yet.