I had a tweed Blues Junior in 1996 and was not particularly impressed with it. It just sounded like a small weedy amp. I sold it and bought a Blues DeVille - which I really liked.
This Mark 4 Blues Junior is night and day different. I am sure that the 12" loudspeaker has contributed much towards its 'grown up' sound, but I suspect that Fender have essentially taken a Blues Deluxe circuit and removed a few features (Drive option, Send & Return etc.) to reduce the physical size of the circuit board in order to give this little amp a very impressive authority.
It stands up surprisingly well against my 2002 first generation Bad Cat Cub llR, only lacking a bit of definition in the low mids - which may well be addressed with a better 12" loudspeaker.
Really nice little amp and man enough for small stages, not just hiding in bedrooms like the early version.