Well, you can see that the non-mercenary version is almost identical to the old BiP Melee Support, while simply also incorporating a non-melee version. Both builds were intended to be for players without mercenaries and without Zei Ri. From what I recall, the "Offensive Mesmerway" is simply a merger of the old BiP Caster Support and BiP Melee Support builds.
The Mercenary Mesmerway is then an improved version relying on at least one mercenary hero. Since many people do not have mercenaries (and most characters do not have Zei Ri), there is value in having both versions available. So generally, one would assume that the mercenary version is stronger (though note that there might be situations where the additional mesmer would perform worse than the minion master).
EDIT: Well damn, I took too long to fix my typos.


































































































































