The Creekside is differentiated in many small aspects over the Black Rock. Nicer cabinetry on the Creekside. Raised panels on the refrigerator on the Creekside and flat panels on the Black Rock. Better tires and wheels on the Creekside (although for 2014 they may have brought them to parity). Extra skylights on some of the Creekside models. Creeksides all have shock absorbers, Blackrock doesn't, at least on the models I've seen.
Creekside has options for double insulated windows and solar panels; Blackrock doesn't. Basically the same floorplan with lots of little extras and options. The frames and wall build quality should be the same for both of them.