Uses less battery: SMS messages take less power to send and receive than network data.
+
+
Better responsiveness: unless an app maintains a constant
+ connection to a server (which would make it a huge battery hog) it
+ will usually receive SMS messages more quickly than other types of
+ data. So you'll see a move right after your opponent makes it.
+
+
Doesn't use your data plan (but per-message costs will kill you
+ if you don't have unlimited texting!)