I think the pro arguments would include privacy and scripting related side chains, and a place to test upgrades in bitcoin that carry economic weight in bitcoin. I'm of the opinion we should first really find consensus on covenants, cross input signature aggregation, upgrading tapscript and stuff, and allegedly we really haven't finished exploring what tapscript gives us today so that would be a good start. I worry that drivechains would disincentivize upgrades to bitcoin itself.