They are pretty similar, and no doubt a lot of the circuitry is the same. HOWEVER, the V:25 tends to be very compressed due to its low headroom, and it lacks lows and highs, as the EL84 is much like EL34, but with even less lows.
The JP-2C has way more headroom, so it's clean channel is cleaner and the lead channels have way more dynamics and transient attack. It doesn't get super compressed, rather, you can add gain and get more harmonic content, but still get a lot of definition. It's 4x6L6, so it really is a completely different animal.
In particular, I found the V:25 IIC+ mode to be a bit anemic, where the JP-2C ROARS.
However, at bedroom levels, or recording via the CabClone, you could probbaly make do with either, though again, for CabClone recording, the 6L6 still has way more dynamic response.