I think (IMHO!) that some of these picks that are made of different materials than normal, SOUND fine or even good, as long as you keep you pick flat with the line of the string. As soon as you start angling the pick, the material related side effects start to creep in. Acrylic chirp, metal zing, etc. I can fly on my Taylor 614 with a V-pick, but the chirp drives me crazy. Can't put up with it, even for the easy speed. Had the same effect when I tried the "Big Stubbies" years ago. Like a scene from "The Birds."
The shape of the edge of the pick has a big effect as well. For example, my longest running "standard" pick I can use for anything is the green jazz sized Tortex pick. Those are great playing and tonally. They do wear though and after a while, the point is rounded and the edges smoothed. I keep one in that state and one new one on the bench at all times, and if I use one, grab the one I want, knowing they're no longer identical in feel and tone.
Re: pick edges, I like rounded off, rather than straighter edges with angles. I have a V-pick that has angled flat edges that come together in an edge that could cut your finger. I much prefer the ones with rounded edges. When you're picking fast and changing strings, you need the pick to glide over the string, and not have a "grab/pull/snap loose" type effect. The later gives you more attack, but makes it much harder to glide over the string when picking fast.
This again is where player preference kicks in. I have a friend who plays slow, old school blues. He uses big thick strings, and big thick picks and medium high action. He's only playing a few notes and never fast. His guitar setup doesn't work for me.
If you heard that Happy Birthday thing I did messing around a couple years ago, I think there are about 45 notes in the first (just under) 4 seconds of the song, and every note is picked. For me anyway, I have to glide effortlessly over the strings in order to do that. So I need a point, but not too sharp, and smoother rounded pick edges.