There are no two properties which are "exactly" a like, even if they have the same floor plans.
The fact that one is locating in Porter Ranch and one is in Granada Hills, the one in Porter Ranch will tend to command a higher price because one community is newer and expanding and the other is established with fewer expansion plans for the community.
If you are a buyer, it is better to focus on the "features" that you want in a home then compare those features with similar properties in the "same" community. This is called a Comparable Market Analysis (CMA) and you could ask a Realtor to provide a current CMA for you.
You can send me the details of your subject townhome and I'll prepare a CMA each for Porter Ranch and Granada Hills for you.
Phone: (888) 525-0125