The is extremely subjective, as the finish/texture can make a huge difference.
I don't really have a favorite, but I generally dislike G-10 and FRN/Grivory, etc. There are always exceptions.
Generally, if the knife has good ergonomics, I prefer smoother texture. This is why the ironwood scales work so well on my Manix 2. The knife is extremely ergonomic, with lots of jimping, and so a smooth wood scale works perfect. However, these would not work so well on something like an OTF.
My mother absconded with my Yojimbo 2, but it had some inexpensive canvas micarta scales with GITD Punisher skull (bought them on the 'zon) and they were too rough in my opinion. However, the burlap micarta is great on the PM2.
Same thing with carbon fiber.
I generally don't like rough/abrasive texture, but nor do I like too smooth.
My favorites would be wood, micarta, and carbon fiber. Don't care too mujch for titanium to be honest. Aluminium is ok in automatics, but otherwise, no thanks.