Hi! Taijutsu and Ninjutsu Pen is highly dependent on you and your opponents stats. The reason is because Taijutsu Pen is the Taijutsu damage that ignores defense. While Ninjutsu Pen is the Ninjutsu damage that ignores resistance. Keep in mind that this value is also affected by the Damage Reduction stat.

Some players feel that Tai/Nin Pen is very helpful when you are higher in battle power, while others feel that the other stats are better.

~Jib