Well, the newer versions of ZBrush seem to have more control over the polycounts of the work you''re doing, still there''s probably noone on earth using that program for doing game models.

The problem i see with it is that ''painting'' models makes it hard to keep control of where the polys go, something quite important on low poly modelling.

If the RPG game is in 3D then you NEED low poly models, wether you do them with max, ZBrush or a fork doesn''t really matter, as long as the output has the desired look and polycount.
You have to know the poly limits of the engine to know which is the best way to go.

If ZBrush can export the models to a format you can read (3ds, lwo etc) then it''s all about which tool suits you better, and in case it''s ZBrush, you''ll probably have to test it a bit and see how those new poly functions work and if they deliver the polycounts you need.