25% and 25% for the fans of both teams and they were "tied". No chance of getting a ticket from the other team's ticket quota unless you had been part of the fan organization for long. Heck, even to some regular Bundesliga games you have to be a member of the club to get tickets...
I read that only 6,000 tickets were available for the general public and they were drawn. There are some Finns I know who were lucky and got a purchase right to few tickets, and are obviously going. So yes, I'm confident that it is "neutral" in that sense, though Dortmund fans are usually a bit louder in my opinion.
And yes Bayern has been a better team this season, but during the past few years they've been "complete losers" as they haven't won anything big. They had very much the same team last season, yet they managed to lose to Chelsea in their home ground... This season could be different but I'll give Dortmund a fair chance. I think they learned a lesson in quarter-finals against Malaga.
I'm a neutral fan in this. In the German football I sympathize Fortuna Düsseldorf and Union Berlin since those teams have the same colors as my real favorite here in Finland, and more importantly I've enjoyed going to their games the most.