I would go with the helicoil.
Yup Helicoil.. The thread is M6X1.0mm. You can get a kit from your local autoparts store.I would go with the helicoil.
I assume re-tapping means cutting a larger thread than the original. I.e cut an 8mm dia thread in place of the original 6mm, then use an 8mm bolt.But....how....the material is now stuck in the threads of the steel fastener. It's already deflected and no longer part of the parent material. Only way to fix this is a heli-coil or time-sert. Both readily available on Amazon or eBay.
In theory, a heli-coil would be stronger as it's grabbing more material. I used Heli-coils on brake brackets, cranked 'em down to 90ft lb. No problems.