An off taste or metallic taste may come from a metal tip, the coil, something from the manufacturing process, or the adhesive being heated or attacked by the juice.
Any "muted" flavor, imho, comes from the wick. The wick delivers juice but also acts as a filter. They "gunk up" from the flavor molecules not getting through.
A silica wick is very uniform with tightly packed together strands="muted flavor".
A cotton wick from a cotton ball is not as uniform with looser strands =ZOMG flavor much better. This also accounts for going through juice faster with a cotton wick.
Dripping drips juice right on top of the wick=More flavor.
Not because of magic or how different any of these devices are, it's all about how the flavor molecules (for lack of a better word) go through the wick (or don't).
Just an observation, take it for what it's worth.