Yes, the large bottle has weight, and I notice it when wearing it. But it's not super heavy that I can't wear it all day. The medium bottle is perfect to go with everything. The medium was my first bottle. It very light.
I had tried on the large bottle earlier and thought, no way, it's gigantic, so I dismissed it.
But one day, I went upstairs to the jewelry repair floor (to pick up my engagement ring which I cracked the platinum prongs... go figure... you can crack platinum?

). The receptionist was wearing a bottle necklace, and the size looked amazing on her. It really popped. I asked her what size it was, and she said large. Back downstairs I go to get one.
I will say though the large has weight to it. If I could only have one bottle necklace, it would be the medium. The medium is quite a good size, and because it is a solid piece, it looks bold. My bottle necklaces are still at Tiffany getting the "premium $35 polishing" (vs. the free polishing), whatever that means.

When they come back, I will take a photo of the medium next to the starfish we both have so you can see the difference. I think you will really enjoy the bottle necklace. It's so iconic.