The Atom has more of a focus on waves and maneuvres than the K103 which is faster and better for blasting. For modern freestyle type stuff I figure the K103 might have an edge, but not by much and for classic carving stuff I think the Atom has an edge. The Atom has the ability to run strapless which can be an unusual and fun feel, particularly in slow waves where it forces you to re-think your sailing a bit.
The K103 and the Atom in fact has the same ancestor which was the original Aero 117. The Kode since grew into a faster design, but the Atom is instead a thinner version. So for real wave sailing I'd say the Atom is better. It's still a fast rocker, so it complements the EVO 90 in that way, but with a lot of outline curve and thin rails it will still be very fin in waves and it will plane earlier and be more effective upwind.