While
vosotros is the most obvious grammatical difference, there's also another form that's used only in
Argentina - the vos form. It conjugates much like the
tu form, and for non-native speakers, it is much easier to
understand than to
reproduce. Sometimes it and the
tu form will both be used in the same sentence, confusing things even more.
Example of usage: "¡Vos sos loco!"
Valentín to Molina in El Beso de la mujer araña
Another difference is visible in pronunciation - Spaniards pronounce "s" sounds that do not come at the end of words as "th" sounds.