I cannot speak to the comparison between the 6P LED's output and that with a higher power aftermarket drop-in. I did try the T1 and the 6P LED at the same time. I chose the 6P LED, although the Fenix light was 'warmer' - and seemed a little brighter. I also ordered a Fenix '4 in 1' kit from the Fenix-Store. That's a special combo including the P2D Q5 Premium and a spare L1D battery holder, cap, holster, and switch, along with some other goodies.
I just liked the SF 6P's feel, runtime, and output. I grab it first at night. I know, with those disposable CR123s, it will work - or, in just seconds, new cells on board, it's back at full power. I liked it so much, I ordered a 6P from an evil-bay site to 'upgrade' - and ended buying a P60L for it, making it a 6P LED for now... when Surefire's own high power drop-in appears later this year - I may just get one. I carried a 6P LED in my pocket for an EDC for a while. Size wasn't a problem... there usually is protection in the other pocket.
The Fenix 'kit' allowed me to 'try' a high output Q5 Premium head - rated at over twice the output of the 6P LED - and on a single CR123. It will put out nearly as much with a single AA. I carry it, in one fashion or the other, on my belt now as an EDC, the 6P being in the car. The P2D configuration is neat - but too small for my hands to hold for extended periods. The 6P fits better - as does the T1. At an outdoor, actually poolside, auction last month, I retrieved the 6P as the sun fell below the horizon - no one had thrown the breakers, or knew where they were, so the outdoor lights were off. I loaned my P2D to the event director and I used the 6P LED - we were able to keep the buyers out of the pool - and get the display items to the buyers. I'd say they averted potential disaster - there was an open bar! Oddly, from across the olympic+ pool, I could see that super bright P2D - and illuminate some of the tables with my 6P LED from there as well. The P2D was in my pocket... I had to go to the Jeep for the 6P.
The Fenix 'kit' is ~$67 delivered - the SF 6P LED runs $85. My pair of 6Ps and the 'kit', all bought since Feb, are still on their original batteries, although I ordered a couple of dozen SF CR123s (I may get to test that shelf life!). Either way, you won't miss - both are great products. As a pocket/belt sheath/purse light, the P2D/L1D will always have a home. As an upgradeable, the 6P LED is great - not a bad first choice (Like they told me, there will be more...).
Stainz