The Calypso excels at (in comparison to the Capri) and based on rather expensive upgraded tubes (Mullard 10M NOS tubes):
Better bass control, coverage and definition
Better sound staging with larger scale music - Capri can collapse a little bit with larger scale music in comparison
Better focus within the sound stage, perhaps it just better air with the Calypso
Better balance across the sprectrum, but this is very close.
Personally, I think I like the high end better with the Capri, but I feel this is Jeff Rowland strength.
I felt both handled most things more similarly than differently. Both are smooth sounding preamps but still deliver very good resolution. Neither are bright by any degree in my system. The biggest difference between the two is the bass performance and the sound stage. The Capri is pretty good with the sound stage, but not to the level of the twice as expensive Calypso or 50% more expensive Calypso (if buying used) - factoring in upgraded tube requirements.
For me, with the integrated HT, the Capri is just so much easier for my family. Accoustically, the Calypso is better, but the Capri is pretty darn close.