I have a TransGo kit in my 89 Mustang AOD and a B&M Transpack in my '65 Fairlane C4.
The Transpack shifts MUCH harder, to the point of it almost being probably too harsh (not necessarily for the transmission, but as a daily driver).
The TransGo kit corrects a number of the inherent problems with shift characteristics of your transmission, and will extend rpm between shifts, etc. just like the B&M kit, but it is not nearly as hard. Firm, but not neck jarring hard.