What exactly could be different in 10 years with the clerkship than without
Are you referring to partnership chances
First, you'll effectively be closing certain career doors -- academia, USAO, etc. And if your grades are good enough that you can be confident of landing a clerkship ITE, those very easily could be options.
Second, in certain niche practice areas, a lot of attorneys look down on colleagues who didn't clerk. No, they're not big areas, but they tend to be disproportionately fun.
Third, a temporary one or two year job in a random city is much easier to swing when you are 25 and just out of law school. It can be very disruptive when you are 30 with a spouse and a kid and a house and a midlevel associate job.