I like both characters. Sure Tashigi is in current chapters, but not as a major character.
As for people saying Zeff "is no irrelevent", some shay he's "now irrevelent", others have said his character is. It just convinced me to to vote Zeff.
So what if we've not seen Zeff for a while, that just makes him "unimportant to current storyline", that is different than sayign he's irrevelent. Saying that gives the impression that Zeff is not important at all.
If Tashigi was out ouf the story, her character not exist, nothing would change much(except some fanservice), the story would not get a big change. Biggest change is who arrested the unconcious Crocodile. But take Zeff out of the picture, and the line up of the Strawhats would change as Sanji would be dead.