I own both and I think my 2D rebel maglite gives the tle-6ex a run for it's money. It is as bright if not brighter. Neither are great though. The rebel maglites still have the same heatsinking problem that the luxeon III maglites had/have. I did a simple test with a multimeter and measured the starting current from the tailcap. Right when the light is turned on and cold, I read 1.6A and after 20 minutes I read half that; .83A. The tle-6ex have the same problem of little or no heatsinking, but from my understanding have been designed to run at the edge of burning up and no more.
The worst thing here is the pickle you're in with these new rebel maglites. If you buy one and don't like the LED in it, you can't take out the old LED drop-in like you can/could do with the luxeon III maglites. Take a look at the maglite upgraded to a rebel thread for pictures of the new
design. You can still cut the cam off and use the switch for modding though. If you really want your 2D maglite to be the brightest it can be, you can't go wrong with one of Gene's drop-ins. Modify your 2D maglite to accept 3C or 3AA cells, use rechargables and you'll have a great light.