Hi - for me, it is really up to the recording you happen to be listening to at the time. Since you can switch back and forth between the two modes at the touch of a button, you can decide for each recording which mode you think it sounds best in. I haven't found a really regular pattern. Generally speaking, in a recording with a vocal soloist, the soloist will usually sound better in the triode mode, but again, this can be recording dependent.
Another thing to note is that it is not a true triode - the tubes are still pentode tubes, being made to operate as if they were triodes. So it will not sound exactly the same as a true triode amp. It is fun to play with the two different modes, though.
Another thing to note is that it is not a true triode - the tubes are still pentode tubes, being made to operate as if they were triodes. So it will not sound exactly the same as a true triode amp. It is fun to play with the two different modes, though.