I've actually owned an S3 AND an S4.
The dude ALREADY HAS an iPhone. I'm guessing he's well aware of its limitations already. That's why I never mentioned it.
If he's thinking about buying a Samsung, he should know what he's getting.
All of the "pros" you mentioned are not only had by Samsung but by a great many other Android device manufacturers. Removable batteries and additional storage aren't unique to the Galaxy S.
The big difference is that a lot of those other manufacturers aren't asking you to invest not only in Google's ecosystem (a fact of life with Android) but ALSO with Samsung, because Samsung wants to use their phones to hook you into buying Samsung TVs, Samsung BR players, Samsung PCs, and everything else.