If you Check out the armor fundemtals advanced guide made by one of the game Designers,
heres the link; (sorry not sure how to make this a clickable link)
http://starwarsgalaxies.station.sony.com/content.jsp?page=Advanced%20Guide%20Armor%20Fundamentals
Quote: "Stun damage is the bane of armor, player and creature alike. Most armor is vulnerable to this Damage Type. Fortunately, only a few weapons such as the jawa ion rifle and the tangler pistol deal stun damage. Fencers are also known to use stun batons."
then it goes on to say;
Do Personal Shield generators work the same as armor?
Yes, they do. There are some differences, however. Shields have no encumbrance penalties and act as a second layer of armor. Damage is first absorbed by the shield and whatever remains goes to the armor. Shields also have an innate protection against Stun damage which no other crafted armor has. The trade off is that shields are extremely fragile. They wear out quickly, making it an expensive proposition to use them continuously.
My point to telling you this? Like I have stated in a few other posts, It goes along way for the armorsmith to educate thier customers on what type of armor they should be using in which scenario's, but in the end, the player is the one that chooses his/her gear.
Take PvP for example. you never know what your going up against most of the time, so of course if you have a set of Advanced composite with 80% special protection Vs. Kinetic and Electricity, and a Base Effectiveness of say 66% sliced up to 80%+, the only thing your not protected against is Stun dmg, hence equipping that Imperial test PSG with a 46% base sliced up to 60%+ vs all but Energy.
Wearing this combination of armor and PSG gives the most protection vs all, and so, if you can afford it, kinda makes sense to buy it and wear it right? The trade off is simple. In order to wear this armor, there is no doubt that you must be buffed. The armor i have just described is the the heaviest and most encumbering in the game.
What alot of people don't realize is this;
the trade off for wearing a lesser set is simple, sure you may only have a 40% vs kinetic or energy for example, but, with a difference of anywhere from 500-800 encumberence to each substat, you are going to regenerate your pools at a ratemuch faster than if you were wearing comp. you are also going to get your specials off and regenerate pools faster, be more accurate in your hits due to less encumberence, and be more able to dodge alot of attacks (given you have the skills). the idea of this goes out to Melee classes whose special attacks in the high end of the class use a large amount of stat point cost. Powerhammers for example use 100+ health points per special.
What i have found is, Players are lazy. they don't want to figure out what armors are needed for what situations, so in the end thay only want Ubese for PvE creature mobs, and Comp for NPC's and PvP. It don't take long to make money in this game, and once you have Ubese, you can do missions faster without having to heal or waste time with incaps etc, you just last longer, so you earn your money for Comp even faster. Once you have Comp, people can rake in 100k in an hour or 2 easily and therefore it only makes sense that you would save up for another set. This is what kills the other armors from holding thier own. Plus the fact that once you have that composite armor on, when your buff wears off, your stats are modified to 1/1 if the encumb is beyond your limits and you don't have to take the armor off. So you now are still protected 80% vs everything but Stun, unbuffed, even though it would take 20 min to regen your 800 hitpoints, people don't care, they will find thier doctor and get buffed again and then drink thier Varsarian Brandy until the cows come home.