Well I have seen 6 DT gigs now since 2007, and while I have enjoyed them all, I did personally feel like the new lineup just had a bit more energy, and just seemed to be more relaxed and noticeably enjoying it a bit more throughout. I don't think it was a monumental shift at all, and I can remember many hilarious times with Portnoy as well, but it was just a more consistent in the current line up.
I'm a big LaBrie fan as well, so for me, it was nice to see him take on the front man role more prominently, and his stage presence was much improved. And mangini was thoroughly enjoyable to watch, not as crazy and as interactive as Portnoy, but he was constantly smiling (or pulling a variety of other hilarious faces), and interacting with the band, or pointing down into the crowd.
In summary, I love both lineups, and while I think there is little to choose between, I feel the band as a whole has more presence and enjoyment now than before, but only by a tiny bit - and needless to say, this only reflects my experience, at those gigs with those crowds, they will have good and bad nights irrespective of who is in the band.