None of the above?
IMO, I think it would be a disservice to recommend "most common" DCs for ability checks in 5e. The DC should squarely be something the DM calibrates based on the approach and goal of the PC as presented by the player. That is, assuming there is an uncertain outcome and a meaningful consequence for failure of said approach and goal. I do like the suggested DCs for using tools presented in Xanathar's - and I think those are examples that aligns nicely with the PC's approach and goal.
That said, I believe there should be some guidance in the DMG - by way of example - on how/why to set easy (10), medium (15), or hard (20) DCs. DMG pg 238 does a reasonable job of starting this but strangely abdicates ultimate authority to the adventures. So many of the DCs presented in the published adventures, meanwhile, are there to... facilitate rolling dice? That is to say that some (most?) of these DCs exist with no meaningful consequence of failure (i.e. nothing happens) which flies in the face of the rules presented on DMG pg 237. What's is really the point of rolling in those cases?
So, not trying to derail your poll, just coming at this from a completely different angle at our table.