Any reason not to just re-import priv keys instead of going back to old wallet.dat?
Yes. Most users don't know what commands to run in order to get "all" the wallet addresses.
Your wallet has more addresses than shown in the "receive" tab.
Those are new addresses created for "change", which means the remaining of the coins from a transaction you created.
So, if you don't dump and import private keys of all the addresses, you may end up with missing coins.
I had previously made a new wallet and send coins out of my old wallet because it was hard to tell what was missing in every resync. So it's just a short list on my new wallet, easy to import