The biggest difference is the surface chemistry and how it will benefit you.
The dominance of silicon hydride (Si-H) groups instead of the “silanol group” (Si-OH) common to all irregular or spherical Type A & B silica based phases changes the general character of the column; ie solvents will adsorb and desorb differently and much faster producing many benefits.
Your separations may or may not be similar when upgrading from ordinary silica to Silica-C™ as this will often depend on the chromatographic conditions you chose to use with the columns. You may want to develop method conditions that utilize the full power of the Silica-C™ columns.
The greatest benefit to Silica-C™ is that when using it for normal phase, you do not need to control the moisture of your mobile phase solvents to control retention times. Also, since the Silica-C™ column does not have a strong association with water, these columns last longer and equilibrate easier.
In general, these columns are more robust, more versatile (can be used for Aqueous Normal Phase) and more convenient than ordinary silica columns.
While this is true for Silica-C as stated above, it is also true for Cogent TYPE-C silica based HPLC columns.