Ink is right, they are double dipping into the character pools hoping that scale is enough to differentiate them so that people HAVE to buy both.
Those of us that pick and choose, wait for the 1/4 scale, cos they will come out with 1/4 scale versions eventually, but from the looks of things, 1/5 is not such a gurantee.
That's why I'm am saddened by 1/5 scale pieces because they make us wait longer for the 1/4 scale versions, and if they gauge popularity of the characters from 1/5 scale they 1/4 may never be made. Plus we can't mix and match the modern costume versions with the old costumes in the same scale or may never see some of the more obscure characters in 1/4 scale since they have already made 1/5 versions (Hobgoblin)
Most important is for us collectors to stick together no matter what you collect, because this scale discrepancy is deliberately created by Sideshow greed and not as a preference from the collector community. If you support 1/4 scale, avoid the 1/5 scale and eventually they will pile up enough for them to make more 1/4 scale. Don't worry the 1/4 scale will come eventually and most 1/5 scale sells slow anyways so take your time even if you want to order it til the low quantity bar appears.