I have to say that the magic of the DiaLogue Premium running EL34's in triode is pretty amazing. They will both sound good. I would consider the following: Resale value, build quality, and serviceability. Service really means not having to deal with something breaking.
You can go to the PrimaLuna website and look inside to make pretty exacting observations. It may be hard to look inside the Triode 25 but here is a link you can cut and paste
http://www.hifitest.de/test/bildergalerie/roehrenverstaerker/unison-triode_25_9636/8#b
You can go to the PrimaLuna website and look inside to make pretty exacting observations. It may be hard to look inside the Triode 25 but here is a link you can cut and paste
http://www.hifitest.de/test/bildergalerie/roehrenverstaerker/unison-triode_25_9636/8#b