Hi Pat,
UPZ has four models, from flexy to full on stiff, they are XCR, AT8, RC12 and RCR. Each boot has 2 adjustable springs for compression and rebound, plus one can swap those with another set of stiffer or softer (three total choices). Each boot can accommodate 4 different outer tongue choices, from 90, 110, 130 and 150 MFI. For comparison purposes, the XCR ships with the 90 MFI and the full on race RCR ships with 130 MFI. UPZ makes liners for thin feet and shins, regular feet and shins, plus has swappable liner tongues in regular, thick and thin. This is great if one has regular feet but thin or thick shins. New to North America for '24-'25, we are importing UPZ foam injection liners. UPZ makes 4 varieties, all of which can be injected by a good ski boot fitter.
We do full alpine equipment demos all season long here in Northern Utah. We have boards, bindings and boots. We just ran a demo yesterday, which is also an excuse for us to get out boarding.
Ultimately, the best boot for you is the one that fits and performs to your standards. We simply provide the opportunity.