I like to use milestones, keeps unecessary book keeping at minimum. Regarding 5e, I feel the class advancement is too limited. That's why i prefer PF2. I also love Fate Core.
I'm an XP giver myself. It's definitely more work than a milestone system; but I feel it gives the players more satisfaction, feels like they worked for the level
Definitely agree re the class advancement, liked what they did in 4e with the prestige classes or whatever they were called. As it stands, I feel levels 10+ are a little weak
At the same time, allows me to finely tune the amount of XP I grant; so some actions can give more or less XP than others based on their challenge
