[Tomte]

Learn the new default ones.

First, not all veterans stay with the old ones. Second, going forward all learning material and documentation will use the new ones. Third, even those veterans who stay with the old shortcuts for convenience mostly don't see it as a war and will tell you to just go with the "new" flow.

And last, but very much not least: it's a numbers' game. There are quite few veterans (Blender was and still is relatively niche), but a boatload of new Blenderers learning it right now (or having started within the last three years when the UI revamp was released). And many many more than even that boatload of new people will start learning in the next few years.