I've been using white dental direkt zr for frameworks, what do you mean by "best to work with", to me they are all the same more or less, but I'm using only white zr, maybe there would be a difference with precolored zr, also I have no idea would it affect the color, meaning if I use the same porcelain powders for white frame and precolord a3 frame, in my mind the a3 precolored frame should be darker, because white frame has no color, so it's gonna be the color of whatever powders you're using, but the precolored frame already has the color and if you add the same color - it might end up looking darker, but once again I have no clue, just thinking out loud