So what's the precedent for which post gets the parent? The older but lower quality post #362634 that has favorites, or the sharper, more recently uploaded image here?

Does it even matter?

In this case it doesn't matter, but higher quality is always better.

Hmm... There should be some kind of favorite-transfering system that doesn't involve deleting the child image...

roastbeefy said: So what's the precedent for which post gets the parent?

The parent is the best one, unless they're duplicates, in which case it's the earlier one. Simple as that.
This one is smaller but still probably the better choice for parent. Not a critical difference though.