Picks that are not flexible are widely considered to be the best for fast picking and speed riffs because the tip of the pick is always exactly where you expect it to be as opposed to thinner picks whose tips drift from side to side as they move through the strings.
These thick picks tend to have a smooth release, which means they move easily off the string after the pluck. However, because of their thickness, they also pull the string off-center which can make the pluck feel sticky and render the string position un-dependable.
The good news? There’s an easy fix for all the down-sides of thick picks: play at an angle. Instead of having the surface of the pick parallel to the angle of the string, hold the pick at a 45-degree angle with your thumb pointed down. You’ll notice that the pick moves through the strings like butter. And instead of pulling the string in the direction of the plucks, the pick pushes the string down toward the top of the guitar, keeping the string centered.
[photo: Patrick Hoesly]