This is a very subjective question, because all styles have a good points, I know that Bow isn't a armour part, but it has a relation of my answer. Each Bow Style have a 'hability of arrow' what opposses of strong point of another style, like an initials pokemon weakness of another initial type. For example, the Heavyweight bow has a hability that do % damage when the enemy dodge a hit, this hability give it advantage againist the Dodgers, who have a high probability to dodge.
But in my opinion, for my style of play the best style is the Heavyweight, because reduction of damage, and have lot of HP, a fully Buffed Heavyweight can't beat a 5 players in a PvP battle, but can stay him while others wins or preparate himself, because the poison like effects that not scalate in proportion of objective's HP, are less effective againist. In PvE they are good in no gain a lot of experience because the relation of HP and experience aquired.
The second best style armour are the Bonecrusher, no much defense but, high probability of critical hit and high base damage, this combined to effects, amulets or rings what give a chance of stun, do this style great for finish fast the battles, this style it's like a glass cannon.
The third type of armour, Dodger, have a equilibrium with defense of Heavyweight and damage of Bonecrusher, this style have a lot of builds or styles of play it efficiently but you must know it or it's less efficient than others styles.
I don't know if this is considered as an Style, but Generalist objects appears as a Generalist style, and if generalist is considered as an armour style is the worst by difference, only recommended for new players, wear it its better than are naked.
Thanks.