It seems of all the manufacturers, VW is the easiest about refunding the $500 (after the $400 payment) with just a click of the cancellation button, and a few follow up clicks to confirm (at least that was my experience with my first FE cancellation), and Ford the most risky (some Ford dealers do NOT refund the $500 Mach-E reservation/order payment).
If you can afford to have $500 tied up for a while, best option would seem to be keep your VW option open. We might know the rules for any changes to the $7,500 fed tax credit before ID.4s get to the dealers, at least the Pro versions after FE.
OTOH, in some number of months, ID.4 Pro will just be another car on the VW dealer lots too. Another possibility, while Ford dealer are not allowed to sell their "FCTP" demo cars until some number of miles (possibly 4,000 for Mach-E), I got the sense that VW dealers can sell their ID.4 demos (not sure).