  We present a comparison of the noncommutative field theories built using two
different star products: Moyal and Wick-Voros (or normally ordered). We compare
the two theories in the context of the noncommutative geometry determined by a
Drinfeld twist, and the comparison is made at the level of Green's functions
and S-matrix. We find that while the Green's functions are different for the
two theories, the S-matrix is the same in both cases, and is different from the
commutative case.
