I almost ordered the Fenix PD20-R2 looking for a compact but powerful one cell CR123A light for my key chain. I was told that the Quark Mini 123 has the CREE R5 led which is suppose to be brighter and more effiencient than the CREE R2. So I cancelled the Fenix light order. Now I'm hearing that I should have stayed with the Fenix light because it's a better build quality. Supposedly others have had problems with the threads on the Quark flashlights being loose.
The question is what's the better light and why?
CPF's motto is of course "buy both". Did you get the Mini 123? If you like it, what are you worrying about?
Yes some of them do have loose threads. Mine has them, it's a little bit annoying but not the end of the world. Mine is one of the earlier ones and I think they may have straightened out the problem in later production.
IMO any 123 light is too big for a keychain and even an AAA light is larger than ideal. The full sized Quark 123 (not the mini) is WAY too big for a keychain. The Mini might be ok if you like bigger stuff on your keys than I do.
As for the UI, I think the PD20 and the Quark Mini are both too complicated (I don't actually have a PD20 but had a similar L1D for a while). I think the PD20 is also a bit bigger. I have several Fenix lights that I do think are better built than the Quark Mini, but they also cost more.
If you get either of these lights and don't like it, you can sell it on BST for about $5 less than you paid for it, so it's a cheap enough "rental".