No experience w/Glock light, but they seem bulky compared to Surefires & Streamlights. Also, no experience w/TLR, but my dept issued Streamlight M3 is not very water resistant and has failed me a couple of times on tactical operations (thank god my MP-5 had a foreend Surefire and a collapsable stock).
I've carried Surefires for all of my 10yr LE career and wont carry anything else, with the exception of the issued M3, which I'm trying to change.
LED units from Surefire (and other mfg's) look very promising - I'm holding out to see longevity on the LEDs (our squad cars have LED light bars and our city has alot of LED traffic lights and have had some problems with early failure - but they were not made by Surefire)