Rhododendrons and azaleas both belong to the genus Rhododendron. Azaleas make up two subgenera of Rhododendron. Mostly, small leaved Rhododendron (genus) are classified into one of the Azalea subgenera, but this is not categorically true, and there are some smaller leafed Rhododendrons (species).
I'm not an expert, but the leaves do look pretty similar to a typical azalea, but appear larger, as you pointed out. Not sure that helped, but I'd suggest asking a local nursery for a suggested ID, as they will be most familiar with local landscape shrubs, especially if you can find an older employee. (That shrub looks like it's been there a while)
Based on just a tiny bit of online searching, it seems that the easiest way to Identify the species (if it's an azalea) is by it's flower (color, shape, composition, etc.)
http://www.tjhsst.edu/~dhyatt/ars/natives.htm