So part of the switch to canon meant I could downsize my filters to 4″x6″ panels.  The sigma 12-24mm and nikon 14-24mm both needed X pros in order to work.  The 11-16 I have now and the 10-20 I was considering both work well with Zs which are smaller, cheaper, lighter, but more importantly available from more manufactures than just cokin and the other filters are more neutral.  There are also a lot more options.  But the issue I have with the Zs is the filter holder.  It’s very cheap feeling compared to cokin’s own X holder.  The Z is soft bendable plastic and it’s a bunch of parts screwed together.  The Xs are much stiffer and don’t have all the parts which makes it much more solid.  I had to modify the Z holder to work at 11mm w/o seeing the holder at all, but it’s an easy fix that actually makes it smaller again, and only takes 3 minutes.  I then sanded down the bolts and plastic pins so it’s a much better fit now.