The the biggest difference between the to is the placard system that the lpc uses, not so much of an issue if you only use one platform but if you dont then the placard system makes changing a loadout much easier.
I have used a dcs but now use a rpc carrier, with the placard setup. I keep the appropriate setup in the case with each rif. So if i fancy a change or somethings fails it just rip it off and slap on the new one.
In regards to using the sides to replicate the belt selt up, unless you have pouches which have harder mounting material or clips, and need the padded sides, ladder sides still take molle pouches but with a bit better air flow and less weight as you give up the side armour pockets.