Due to its form, gauge transformations for the typical electrodynamics potentials are "local" in nature. That`s: they exists for path connected topological spaces. So, there exists global gauge transformations or are all of them local in nature?. If the answer is "yes", i.e. if there are global gauge transformations our ideas about electrodynamics are quite general, if the answer is "no", then we cannot have a global equivalence of the different gauges, and the results obtained in one gauge are not globally equivalent to the results in any other gauge. What do you think???.