If you have two 0.0.0.0/0 routes and one is nonesense, what percentage of packets are doomed to oblivion?
whichever is higher in the routing table wins, doesn't it? Or would next hop come in to play to decide how local destination was?
I find most kernels use round robin on two identical next hops.
in any case, if one doesn't work, it's not going to work.