I feel very confident that I can draw upon my experience to dial in a cue mix for myself that reflects what I need to play well. I'm sure that WW can do the same.
In a tracking situation, a static balance is what I prefer. If I cannot comfortably play to a static balance, something is FAR wrong with either the arrangement or the group dynamic, and that needs to be addressed, not disguised. In fact, the single biggest annoyance to me, as a player, are levels moving around while I play. It makes it impossible for me to truly know what the relationship of my part is to the other parts (timbrally, temporally, aesthetically) at any given time, and frustrates me to no end.
The real disadvantage of the personal mixers is simply that many players, particularly lower on the experience scale, don't have as much audio/mixing experience to draw from when making their own cue mixes (and, as WW pointed out, are often playing to different things).