The main difference I noticed with the RBZ shin guards vs the CLs is that they have Lycra straps instead of standard elastic straps. To me the Lycra straps felt like they allowed me to get a tighter, more secure and also more comfortable fit with the RBZ pads than I remember being able to achieve when I tried on the CLs last year. In this video the CCM Protective Line Manager mentions the changes in the RBZ shin pads starting at about 1:20.
She mentions that the shell better aligns with the knee cap and that they revised the strapping system and how some of the foams fit so you get a closer fit. Based on this, the tweaks in the shell along with the strapping likely both contributed to the more secure and comfortable fit I experienced vs. the CLs.