Hi Quintrex, As you probably know, I often refer to German photo mag ColorFoto. They test in a lab under carefully controlled conditions, always using the same cameras and exact same targets, and overall making sure things remain comparable. Problem is, they did not test the Nikon 105 with VR yet.
Nevertheless, there are hints: on Nikon's D800, the Sigma received the highest score they ever awarded to a macro, an 88, which is 17.5 points above average across all lenses for Nikon. Nikon's predecessor lens, the 105/2.8 VR G ED Micro, scored a measly 65.5. Because of this, I find it very unlikely for the new VR version to outperform the Sigma. For comparison, Tokina's 100mm got 79.5 points, no slouch either but not quite at the Sigma level.