i assume you are talking about the boots. The XXX is really stiff, and the X is softer. I personally would go with the X because i like a soft boot, but it is all by choice. I'd say try them both on and see what fits you better, flex them a bit and see what seemes nicer to ya.
'now the rule of thumb here....'
'RULE OF THUMB! In the early 1900's it was legal for a man to beat his wife, if he used a stick no wider than his thumb!'
'That sucks, you cant do much with that, should have been the rule of wrist!'