I'm not sure. According to IW website and my knowledge, I think the shell has the same thickness, while the liners and foams are thicker, better (doesn't absorb sweat,...) at the higher end models.
Got myself new shins for inline. IW says that they are for recreational level of play but figured out that for inline they offer enoguh protection and are not bulky while allowing agility.
I have Rbk 11k and they're giving me an awfull ankle pain on both ankles (inner side), so I'm thinking about getting RPD MAX. Main reason is because of everything good i read about Alkali on MSH. Can anyone who owns this skates or Justin tell me how is ankle padding on these skates? Is there enough soft material, padding or will be boot hurting my ankles because of hard outsole/boot?