Thanks for the comments. I predominately went with the sharkfin to lower the obstruction with the roof rack when loading kayaks. I'll post some pictures soon of the RRO rack w/ my kayak on top, it would not have cleared the factory antenna.
I actually bought mine from another forum member, I can't speak to ordering via the website. That said, in my research I found that Visual Garage products are available on amazon and much more clearly labelled for 2012 Jeep Grand Cherokee and with available Jeep paint colors. See this link
. The factory antenna has the GPS/Sirius components in the base and the removable mast is used for AM/FM. The sharkfin replace the mast but is installed around the base. The base continues to operate fine for GPS and Sirius. I have noticed worse AM reception w/ the sharkfin, but it's otherwise fine.