It depends. For specs that revolve around maximizing the uptimes of various buffs and debuffs, numbers aren't the best thing for showing durations and cooldowns, because what you're really timing those things against isn't their exact remaining times so much as the other things you're casting. You don't really care about how many milliseconds are left on your Vampiric Touch DoT; you care about whether your next few casts should be "Mind Flay, Mind Flay, Vampiric Touch" or "Mind Flay, Vampiric Touch, Mind Flay". What gives you that information in the most clear and quickly digested way is fixed-time bars in fixed positions (that is, what EventHorizon does).
On the other hand, a Holy Priest doesn't actually want to use Cascade as often as they possibly can; they want to use it as often as they possibly can when there is significant raid damage. For them, EventHorizon arguably provides more precision than they have any use for, and so they might be better off using icons with numbers in the middle instead to save space. Same, I assume, for other healers, as well as tanks and probably some DPS specs; it depends on what your gameplay is about.