When cast steel shot is properly maintained the particles are very round (spherical). Cut wire starts as a cylinder and is pre-conditioned into a shape we often refer to as a soccer ball, meaning it is basically spherical but it is not as smooth as the cast steel.
The peening effects will be similar (compression etc) but the surface roughness will be different (until the cut wire shot becomes very, very round). I'm not aware of any studies that show a detrimental influence on fatigue life due to these differences in surface roughness.
