The results of a detailed assessment of grid discretisation errors in SOLPS-ITER for ITER partially detached divertor solutions in a full metal wall configuration with neon seeding are presented. It is demonstrated that earlier discrepancies seen in the comparison of SOLPS-ITER with SOLPS4.3 can be minimised or even removed by employing a 4× higher poloidal resolution. At such a higher level of grid refinement, both codes reproduce each other with respect to the divertor operational space in terms of target peak heat flux vs neutral divertor pressure. Higher heat fluxes (about 40% for the low-throughput case) are expected from both codes in a similar fashion in the asymptotic limit for the grid resolution. The overall results of the original ITER divertor design studies by Kukushkin et al are augmented in the way that the offset in heat-load can be mitigated with a higher neutral pressure in the divertor. The work presented successfully concludes the benchmark efforts between the two codes for the ITER application.