All the different pick materials sound and feel a little different. I went through a stage where I was trying every different material and shape I could get my hands on. I settled on 1mm thickness in the 'standard' shape. I used Dunlop Ultex for a good while, because I liked the difference in the attack. Gels were similar. Tortex has a slightly muted attack, comparatively. Celluloid is somewhere in between. What I'm getting at is you really have to try a bunch and find a pick that does what you want it to. I take a few different types to every gig. I use different picks for different sounds.