Upgrade +15.

Because you had more defense xD

Well, I never thought I saw any of that Crit hit defense. Also the stat you are mentioning is called Anti-Crit, which can't be achieved if it isn't mainly in the armor or changed with a brown box.

I do not understand what you guys are talking about but...

The higher your weapons are upgraded the more damage you deal with basic attacks & skills.
Higher upgraded gloves give more p.attack & e.attack. Higher upgraded sub-weapon boosts your master class skills damage (when you learn a skill, its written in its description if it relies on gloves or sub-weapon).

The higher your armor is upgraded the more p.defense & e.defense you get. The defenses reduce damage taken by auto attacks & skills, critical strikes included.

Now, if a Fighter has 33% critical hit gloves + 33% critical hit sub weapon, the damage of his critical hit is increased by 66%.
Critical rate is the stat which increases the chance of hitting a critical strike. It is increased by using "Kaioken", other buffs or by stats from equipment.

Anti.critical stats reduce the chance of you getting hit by a critical strike.
Shadow Knights have a buff that reduces it by 25%. I think this stat exists on Jackets, maybe Pants too. It used to exist in scouters and you could get up to 21% Anti.critical on them but then they deleted it with the latest scouter update before the servers shutdown.

I personally think that the game is more balanced at the moment because every class... For example Humans (Fighters, Swordsman's, Turtle Hermits, Crane Hermits...) have as much chance to kill a Shadow Knight as he has.
Before SK's could get around 40% LP absorb when getting hit + around 60% anti.critical combined with properties & good upgrades... Humans and the other classes couldn't even tickle them.