Gear: synced to ilvl 150 ...

In addition to RylorsEgo post "PvP Stat Caps i150"

http://forum.square-enix.com/ffxiv/t...Stat-Caps-i150

not all items give you max stat in pvp.

check this

http://www.bilder-upload.eu/show.php...1440106412.png

its based on party composition aswell, vitality for examplke has different caps with party members

No watch only to the red marks, then you will see that ilvl 160 items are weaker.
I did all screenshots in the same party.

its weaker because its stats are under the i150 stat cap for that item, this is a common thing for many many items

just because you have an i150+ item doesnt mean it will be at the i150 stat caps