Hi Architeuthis,
As someone who owned a Fagor for years and just upgraded to a Kuhn-Rikon, I highly recommend going with the Kuhn-Rikon, especially if the price isn't prohibitive. I haven't had the Kuhn-Rikon very long, but have noticed a significant difference in ease of use and consistency. The Fagor was certainly serviceable, but a bit more fussy. Also, the Kuhn-Rikon releases very little steam, and allows for cooking with less liquid. I've had great results cooking polenta, caramelized carrot soup and garlic confit from MCAH.
My model is the 7.4 quart: http://goo.gl/QwnrJ and the website says this should do soup for 8-10. I can't really judge regarding pork shoulder as I've never cooked one.
Hope this helps, and good luck!
Shawn