I agree with Daffy; for any of the G2s which have accessories [harder to find accessories] their MOC price tends to be only a touch more than their loose and complete value. Its mainly because, oddly, they can show up more often MOC than they can complete and loose. However with the more common ponies which show up MOC a lot then its more just that the value is so low even on the MOC that the difference between loose and MOC seems very small.
They are your ponies and if you wish to decard then thats your call. However, you may wish to try and trade them for loose and complete versions first. However, from personal experience and my Good Weather & Sweet Clover I know thats not as easy as it sounds!
Secret Tale MOC - $14
Secret Tale loose & complete - $7-8
Sugar Belle MOC - $12
Sugar Belle loose & complete - $7-8