The T25-T
seemed to be slightly more efficient than the regular T25 at least originally. The T25-T also has a forward clicky which I prefer. Compared to most XR-E lights the beam is perfect with no dark rings at all, or at least mine is.
TBH though my 2 year old L2D (smooth reflector) throws just as well as my T25-T and although it is not "tacticool" it still has excellent runtime. I would pass on the regular T25 personally and go for an L2D if you can find one, unless you want a perfect beam pattern. I find the twist to change levels can get slightly annoying over time but all in all its still a good light.