This paper studies the problem of IP traffic grooming in optical wavelength division multiplexed (WDM) mesh networks. Two different grooming architectures are considered: (i) IP/MPLS grooming, and (ii) SONET grooming. The IP/MPLS grooming approach provides a fine level of grooming granularity realized via software based implementations, but has router processing related bottlenecks. The SONET grooming approach is realized in dedicated hardware, but is more expensive and typically offers limited grooming granularity choices. This paper also considers multipath routing as used in SONET virtual concatenation (VCAT) techniques. A detailed comparison of the different grooming options in terms of blocking probability, lightpath utilization and survivability issues is presented. The simulation analysis helps quantify the improved performance of finer granularity grooming approaches over the coarser SONET-based approaches