Blue
Ravenous Bugblatter Beast of Traal
So far we've seen a chunk of character creation, and a few spell and rule changes. Even there we have differences.Well, all reports from people actually mixing and matching UA content and new style monsters with 2014 material say that there aren't any issues Greely doing so, thus it seems reasonable to conclude thst is plausible.
Can I pick a 5e feat that hasn't been reprinted? Since it has no prerequisite can I take it as a 1st level feat even though are noticeably less powerful than the 4th+ level feats?
Is a 5e melee rogue using the OD&D light weapon ruling more powerful than one using the 5e light weapon ruling? Definitely, as it would free up a bonus action that the rogues have a lot of use for while still giving two chance to land Sneak Attack.
If all of the casters in OneD&D are moving to preparation and a lot more spells known, it seems like they will be getting a large boost in flexibility, which makes them more powerful than the 5e equivalents.
Remember, the distinction between the two categories is "math is close enough they can work" vs. "freely mixing and matching pieces from both". Feats without prerequisites is one of the places where it breaks down in the second category.
And we haven't seen most of the rest of the game to make judgements on.