Dave, I have both and the 2500 goes everywhere with me.
2500- has replacement parts that I know I can get, It has a cover, It's easy to use "Dummy Proof", and I can turn it off.
Summit- Can't turn it off (unless you take the battery out), don't really trust the little spinny jobber in light winds, no supplied cover and is not very user friendly. It keeps track of plenty of things but if you are using it strictly for Exbal you will wish you had bought the 2500.