Oce/Canon. I'm not sure if Fuji uses the exact same inksets but I would imagine they do, with the exception of the LED models.
And there is actually a third and fourth inkset available for Canon/Oce. 255 is the highest gamut but lowest adhesion, meant mainly for indoor
paper based applications.
Last I heard they were beta testing a new 257 series which would have the color gamut of the 256 and the adhesion of the 258. If it comes out and works well we may consider this option, although I've been pretty happy with 256 for the most part.
I believe CET also has different inksets available depending on what you're looking for. When options are available there is usually a sacrifice in either adhesion or gamut.
I'm not familiar with the other printers but the manufacturers should be able to go over the different inksets available and their pro's/cons.
I haven't played with a ton of metals although we just started printing on anodized aluminum and Octolux. Prep is tricky and I'm still trying to experiment with different chemicals to remove 100% of contaminants.
I know Artbot has lots of experience in this department hopefully he can shed some light on prepping metals.