http://i105.photobucket.com/albums/m204/jlomein/IMG_8953.jpg
Left to right: AAA battery, Four Sevens Preon P0, Peak Eiger (knurling removed/shaved body, 10180 size with QTC), Quantum DD, Modamag Drake, AA battery.
Very happy so far. I personally like the cool blue tint of the Quantum, although colour rendering isn't as good as the Nichia 219 in my Eiger. However, the Eiger is noticeably pink tinted. The beam patterns of the Quantum and the narrow optic Eiger seem very similar (both floody), with the Eiger having a small slightly more defined spot in the middle. Output of the Quantum appears slightly higher overall when compared side by side to the Nichia 219 Eiger. One downside is that the twisting interface is smoother and easier to use on the Eiger.
I'm really starting to prefer QTC interfaces on these 10180 lights. My Drake (three mode twist off and on rapidly interface) is seeing less and less use.
I use these 10180 lights as necklace lights, and in terms of jewellery appearance, the Drake is still best with the shiny chrome finish. The Drake's downside is that it always sits tilted on a neck chain. The Eiger and Quantum both lay symmetrically straight against my chest. Although both have machined stainless steel finishes, the Eiger is shinier and whiter/cleaner in appearance. The Quantum has a much darker grey gunmetal look to it.
In terms of similarly priced 10180 sized QTC production lights, you're looking at the Quantum DD or Eiger (10180 size available from Oveready).
Quantum advantages: more compact, tailstand ability, two optional tritium slots, battery and charger included.
Eiger advantages: smoother operation, high CRI Nichia 219 LED option, knurled or shaved bodies, multiple battery sizes (10180, 10280, AAA, 2xAAA)
For most, there's very little reason to choose an Eiger over the Quantum DD.