Fenix PD20:
Utilizes a Premium (R2) Cree XP-E LED with a life of 50,000 hours
Two modes of output, selecting 6 levels by turning the bezel
General Mode: 9 lumens (35 hrs) -> 48 lumens (7 hrs) -> 96 lumens (2.8 hrs) -> SOS
Turbo Mode: 190 lumens (1hrs) -> Strobe
Max beam length: 135 meters
Digitally Regulated for Constant Brightness
Uses one 3.0V CR123A battery (not included)
78.5mm (L) x 21.5 mm (D)
Made of durable aircraft grade aluminum
Durable Type III hard anodized finish
39-gram weight (excluding batteries)
Waterproof to IPX-8 Standards
Toughened ultra clear glass lens with AR coating
Push-button tail cap switch
Capable of standing up securely on a flat surface to serve as a candle
Anti-roll, anti-slip body design
Batteries not included
Includes a lanyard, two spare o-rings, body clip, and a rubber switch boot
Nitecore EX11:
Unique electronically controlled "Smart PD" switch - designed for reliability
'Infinitely Variable' digitally controlled brightness system
Intuitive and simple user interface
Strobe and SOS functionality
Military frade aluminum alloy construction for strength and durability
Compact and lightweight - suitable for EDC (every day carry)
Mil-spec type III hard-anodized
Impact resistant in accordance with US Mil-STD-810F
Waterproof to IPX-8 standard, underwater 2m
Broad voltage fully regulated circuit - compatible with numerous battery
chemistries such as Li-ion and NiMH
High intensity Cree XP-G R5 LED with 50,000 hour life and maximum output of 200 lumens
Ultra clear impact-resistant optical lens and computer designed metal reflector
Military grade 550 parachute cord tactical lanyard
Ability to tailstand for use as a candle light
Dimension: diameter 21.5mm, length 76mm
Weight: 44g
Included accessoried: Lanyard, spare waterproof O-ring
Runtime:
Maximum output 200 lumens, for about 1 hours
Minimum output 5 lumens, for about 80 hours
Strobe output of 200 lumens for about 2 hours
Judging from the Amazon reviews, the Fenix PD20 is more popular and is rated higher. However, I would recommend a look at the 4sevens Quark X AA, which is brighter than both of them and runs on 2 AA cells. Admittedly it won't run as long, but that's the price you pay for more power. Another thing is that most manufacturers will rate the power of their lights by lumens at the emitter(the light that is supposed to be emitted based on current), while 4sevens rate their lights by lumens out the front(the light that actually makes it out the glass lens). That usually means that other lights aren't as bright as they claim to be.