Also where you hike matters. I've used my pliers twice to pull cactus and dagger plant spines from my shin and calf. Those spines are about 1mm thick and about an inch long. Tweezers would not have worked. Also, in my ham radio hobby, pliers are essential out in the bush.

If you want a third option, wander into a Radio Shack and check out the Leatherman Squirt they sell. It's for electronics and has a really nice tweezer built into the thing. What would normally be pliers is a combination wire stripper/plier/scissor thing. A very nice tool, and nobody talks about it.

When going for lighter weight, I'll carry a Swiss Army Classic. I've modified the scissors to cut wire by grinding a tiny notch in the blades close to the pivot point, similar to a bicycle cable cutter. That notch can be used to grip things like cactus spines in a pinch. It will cut right through a guitar string!

For super all out light weight, a single edged razor blade works fine...not much good on spines though.