like vesta and morrigans are better than  bandos and 3rd age range gear at pvming...

I think thats because of the bosses def. Weak monster has weak def, strong monster has strong def.
Players just has 99 def max and depending on what armor they're wearing, that's how much you will/can hit them.

It's because regardless of what it's “Supposed” to be used for, pk gear has much higher stats than bandos. There are no other reasons.

It's because regardless of what it's “Supposed” to be used for, pk gear has much higher stats than bandos. There are no other reasons.

This.

I think it'd be better if there was some sort of activation of their bonuses. For example, if the enter the wilderness, it's suppose to be strong and when you're out of the wilderness, it isn't.

There is no pvp gears or pvm gears.. there is nuub gears, good gears and pvp items (vesta, zuriels,..) 

Normally ppl prefer str over def in pk tho..

"pk gear" vs "pvm gear"

Gear is gear. Any gear can be used for either. It just so happens that when players go into the wilderness, they want to have any advantage they can get, which usually means hitting higher, which translates to vesta, etc. It's easy to do this because you arent taking many hits and the gains make up for the costs  (if you dont die). This advantage doesn't matter as much in pvm since you dont have to hit as much. That's why most people will use bandos when killing bosses. They tend to have minions, so you're getting hit often, which costs a lot of money to fix. If you go a long period of time without getting a rare drop, you'll end up losing money through fixing your armor.

I understand what people say when they designate armor pvm vs pvp, but I personally don't agree with those labels.

Pvp gear (assuming you're talking about the armours/weps that spectrals drop) has quite the HUGE repair cost to it.
It'll cost you money to use the armour, and you'll never be able to trade it once you use it. While on the other hand, bandos you'll never have to repair and you can sell after use.
Both have pros and cons.

Because it's the best armor in the game but is supposed to be too expensive to use for pvming at a profit. The reason it is considered pvp armor is because in runescape it will degrade after a certain amount of time and will be gone forever. Alternatively on Emps-World you have to spend an exorbitant amount of money to keep it from degrading.  I guess the cost isn't enough to outweigh the benefits so it's currently viable to use pvp armors for pvming.

"Pk Gear" has a much lower defense bonus than "Pvm Gear", despite it's amazing strength and attack bonus. Having said that, using PVP armous for PVM is very expensive due to the amount of ancient energy being drained in the process. It is highly recommended to use proper PVM armours during boss fights such as Bandos and Third Age regarding the maintenance costs of PVP armours. Trust me, Statuis and Vesta degrade MUCH faster than you'd think..