Stability in the hand
A thick pick bends less than a thin one. For players who want a consistent reference between thumb and finger, that stability can make the attack easier to repeat.
Mass is only part of the feel
Shape, grip, tip and bevel all matter. Two picks with the same nominal thickness can behave differently when their footprint and edge are different.
Listen in context
Try a candidate at rehearsal volume and across both rhythm and lead passages. The most useful pick is the one that stays controlled when the music becomes demanding.