Aside from cosmetic differences such as the list of credits and contact information, the only real difference between Sierra's 8.5.1 and Genealogy.com's 8.5a is that 8.5a (with patch) displays the Easychart color box fill palette correctly.
There is a workaround for that with the Sierra version but people may perfer not to bother with that.
Genealogy.com offers no support for the Sierra releases and Sierra customer service no longer supports them.Sierra has decided to keep their message board up (they twice announced plans to close it).
I've had to go through several software transitions (and near transitions - when Leister dropped Reunion for Windows) in the course of my genealogy research.Change is a fact of life with computers.
That's one big reason I wish there was more progress in coming up with a versatile database interchange format.Gedcom is very much in need of an update ;-( [Not that an update will help programs where development has stopped or virtually stopped...]