Two Venom Shocks(neither one being the VS Pearl). Different drillings and different surface.
If you can only have two, then make the most of the best ball available from Motiv.
At 1000 surface, the Shock can handle oil just fine. At 4000, it can handle light oil.
Of course, if you run into a desert, then you will have to use your spare as the Shock isn't going to handle a true burnt condition no matter the surface and/or drilling.
With the Venom Cobra no longer available, the rest of their current line up is pretty condition specific. But if you can find a Cobra, then go with a Shock and a Cobra.