Are all agents identical except for their abilities?
Solution 1:
There are no differences between the agents outside of their abilities. All of them will have the same movement speed, weapon handling, and hitboxes.
Each agent gets four unique abilities and one ultimate, and each agent can be categorized as one of four types: Controller, Duelist, Initiator, and Sentinel.
So outside of cosmetics, abilities are the only reason to choose one agent over another. Ideally each team is comprised of a blend of agent types that make up a well rounded team.
Solution 2:
Jett can jump in a pretty unique way. That's one thing I like. There is no agent who can jump slowly like Jett and make a soft landing no matter how high you go. And this is not one of those 4 abilities that you need to 'activate'. It works all the time.
There is no difference in normal movement speed.