Side by side, there is a difference between the dual and triple. Plus 150w is not that much louder than 100w. It's not half again as loud.
To get *any* tube amp to really shine you have to turn them up. If you can't turn the amp up, stick to a modeler, it will work much better at bedroom levels. That's what I do - I have a RoadKing, Powerball and 5150 at home, and I use the POD XT the most. :Spin: When I want to make a "real" recording I crank the amps, when I want to noodle around and write or practice, I use the POD.
There is more cost to the triple, the tubes are more expensive to replace, but there is a sonic difference.