It's not just about price per unit
Plastic barrels almost always win on a straight per-unit comparison, and for single-event giveaways with a short shelf life, that's the right call — nobody needs a metal pen for a one-day conference table drop. The comparison changes once you're thinking about a pen that's meant to survive a desk drawer, a bag, or a glovebox for a year or more.
Where plastic wins
Light, cheap, and the imprint area is usually larger relative to the barrel — good for a logo that needs to actually read at a glance. Clip strength varies a lot by model, so if the pen is going in a shirt pocket or bag pocket repeatedly, check the clip spec, not just the barrel material.
Where metal wins
Weight reads as quality before anyone even clicks the pen, and a laser-engraved logo on a metal barrel doesn't wear off the way pad-printed plastic can after months of pocket friction. The tradeoff is a higher minimum order on most metal lines and a longer lead time on custom colors.
The real question to ask
How long does this specific pen need to survive, and where does it live day to day? A trade-show giveaway and an employee-anniversary gift are different problems even though they're both "a pen with your logo on it" — pick the barrel material for the second use case, not the first one you think of.