The "SA" cabin space is larger than "SC". Some "SC" have very large wrap around verandah. They are quite popular but DH and I much prefer the midship "SA" cabins.
I've just read that some of those "SC" cabins are going to be recategorized to be "SB" and will have a higher price. HAL sees some people like those cabins enough to 'presumably' pay more for them.