Jean-Yves Couput wrote an answer about Salomon Shogun Ski Boot - Men's on May 6, 2010
Oups, sorry for the late answer, but I've been a lil out of the BC.com website for a while. Here are the answers to your questions by our Alpine GURU Mike Aicher:
The boots have the exact same shell lasting and fit, but the liners are a bit different. Ghost will be a bit more comfortable for all day fit, and the X3 will feel more like a race liner (more precise)
Either boot will allow for some bootfitting over the instep, if necessary, to fit the arch area precisely.
The shogun will be lighter (2 buckles) and will therefore be a bit more nimble, for skiing in trees and bumps, but a X3 will feel more like a top performing race boot, with power and precision. It depends on the skiers preference. As for which shell size, you should have a bootfitter take a look at your foot inside the shell, and determine which is the proper fit.
Both the Shogun and the X3 have a Boot Sole Length of 326mm in size 28.5, and 336mm in a 29.5. It is likely that you will be most comfortable in a size 29.5 from us.