Yes, it's better. Better output transistors and more powerful transformer mounted off of the PCB (less noise). Also, the tubes we had at ATL were a miss--match with the amp configuration at the time. I think it sounds very, very close to the T5 from the year before: maybe a tad less soundstage, but better tonality, deeper bass with the same microdetail up top. At the same time, Doug's design with the PCB and packaging - especially the thermal bar - means the entire amplifier is much more robust than the T3.
This is the guts of the production version: