The only time a study shows that much of a difference in response rates between the two products is when you take patient compliance into account - in other words, Pegasys seems to have easier side effects, so easier to stay on full dose. If everything else were equal
and 2b and 2a were both bonded to a branched PEG molecule, I'm guessing 2b might actually come out a little better SVR, but that's just a guess. Tell your doctor you're a 'Pegasyssy' and want the easy stuff.