Off the top of my head:
1. 1.5 miles in MK, which I do believe is more than in the past.
2. less time at the end for Epcot, a bummer IMO. That final stretch with park crowds is really neat, nice way to finish. I think this also means no final mile drinks? Unless there’s another spot on the course.
3. AK happens two miles later BUT with an earlier start it’s worth keeping in mind for people who want to do Everest (me). Doesn’t appear to be any change in the route. Likewise for HS.
4. Obvious benefit to WDW, despite making this about us, is that crowd management in World Showcase when park opens is much easier.
EDIT: correction for AK, it's two miles later, not one, this year's race got there at mile 15 and it's mile 17 now. So impact for Everest rides might be minimal depending on pace.