I have several Fenix lights, and they've all been solid. The Quarks I own have better output and runtime, and may have the edge in build quality -- I've had no failures, but the Quarks have suffered far more abuse with little cosmetic damage. The moonlight mode available on some Quark models is incredibly handy.

My experience with Maratacs has not been as positive. I had one Maratac AAA (same electronics as an iTP A3 EOS upgrade) where the keyring clip broke off. I also had a Maratac 9290 (identical to an iTP C7T except anodized in green) with a bad tailcap.

Disclosure: I have no affiliation with any of these companies other than as a customer. I own more 4Sevens flashlights than is healthy for any one person, however.