On one hand, synthetic methane is set to be rather important in the medium term future. On the other hand, bio methane is probably the worse greenhouse product at the moment.
I mean, if it's methane but using another process to create it, it's still methane, a very potent greenhouse gas, that's so far hard to regulate and very easily leak unnoticed. It's "better" than obtaining from oil, but still, it's methane.