Tires generally get much more expensive as the size goes up. Especially for light(ish) wheels. Smaller wheels make sense for a lot of reasons. Money (both initially and to replace tires), weight, ride comfort, performance, etc... 18's look better in my opinion, but you have to decide what matters to you!
No...not a clipse fan. "Grindin" is just a coincidence...actually, never heard clipse. Now I'll have to dl some.