In my experience with 4e the game began to crack in the mid paragon levels (15+) and was truly broken in low epic (22+). I've both played and DM'd Epic 4e games and the mechanics just end up getting in the way, there's do much stuff that your character has in terms of powers, items, features and at those levels it all starts to become unwieldy. I have enjoyed those tiers of play in 4e, but they are not the strong point of the system (that'd be Heroic and low Paragon).

By contrast, my 5e experience has been really good at all levels of play. My RL group just hit 19th level and none of us feel the crushing weight of character options that we did on 4e at equivalent levels. In our experience the game remains balanced between characters within the party and fights don't drag on for hours like in 4e.