level kuro or tashigi?

Will tashigi special help more for monster chopper?

It depends on which team you will use. For lion song/vivi I would go for kuro because of his higher damage. You will clear monster chopper faster with him as with tashigi.

You should just go with kuro if you have both. You need lots of damage to take down chopper so the 100 more to have ur multiplier effect is pretty significant. Also tashigi has a really annoying growth model for attack so it takes her a lot longer to even get to her decent attack values.