Try and see, might be different for you...
But...
Most people will find it harder going lower, especially towards the nut. Because the stretch is bigger. Also because around the 5th fret is such a natural place to put your hand. I think that's why exercises like this usually go for the 5th fret as a starting point. Going higher will probably be more or less the same until you get high enough that your hand is having to negotiate the guitar body and the frets are getting to be smaller targets.
I love this exercise, btw. It's a huge challenge for me. I'm starting to get to the point where some days I can get through a cycle or two without blowing it at slow speeds. :-)
Oh, another cool thing to do if you start really getting it, jazz it up! Change up the timing (switch between triplets, quarter notes, eighth notes, syncopate, add swing), switch directions around arbitrarily, etc. This is some advice I got via Victor Wooten once regarding scales. Applies to any route kind of exercise.
Hey thanks router. Is it harder the higher or lower you go?