I'm struggling with this decision too. Are XP awards needed for todays games. When I think about my childhood, it was incredibly important, every amount was critical to calculate precisely and award fairly, otherwise we felt we were "cheating".
But when it comes to todays adventures does it really add value when you have an adventure that expects you to level up once you complete a particular section. Does it make sense when the game shifts from mostly combat to mostly stuff other than combat.
I can't really tell if I am just old and lazy now, and thats the only reason I want to avoid XP and stick with milestones.