The more I play with the Fifteen the more I love it- there is such a sweetness to its midrange even at lighter audible drive settings and I love how relatively subtle the EQ is and how it interacts with the drive character. It sounds nice for chording too (holds things together nicely without too much fuzz), and very dynamic without getting harsh when set around the edge of breakup.
I ended up picking up a Super Vintage on sale on a whim based on my first impressions of the Fifteen and it's been very interesting comparing them (so far mostly through the 1/4" out used as preamps rather than via DI with Cabsim). They are very different, even set clean and "flat"- I was expecting more similarity at low gain given the shared DNA but each has pretty inherent character. I really like them both in different ways- the Fifteen has more of that midrange sweetness and overall clarity while the Super Vintage is generally more chunky in the lows and low-mids and relies more on the Mid control for different response (I actually don't miss the lack of Mid on the Fifteen). The sound range available from the Super Vintage is MUCH broader, alot more fat and alot more top available, not to mention all the mid control. At edge of breakup settings the Fifteen retains that sweetness and seems to retain more dynamics while the Super Vintage gets aggressive/crunchy much faster (this becomes very obvious when digging in while playing chords)- this may just be about not hearing the saturation I the Super Vintage as easily so needing to start at a lower Drive setting to begin with. The Super Vintage low-gain range is definitely smaller and more touchy to dial in (the taper of the Drive puts alot of change in a very small tweak of the control in the area from 9-12 o'clock, the Fifteen low-gain is easier to dial in for me).
They are both really nice. Was hoping I'd have an obvious preference but I'll clearly need some extensive band rehearsals. I feel like the Fifteen will be hard to let go of, it's just so nice to play though even if it didn't end up working in a band mix as well. Keeping both would be an expensive proposition!