I've read and seen a lot about the tamron 90mm, its meant to be a very good lens for the money as is the sigma 105mm.
i have the tokina 100mm and think its on par with the other two lenses.
As far as macro lenses go i dont think there is a bad choice from the top 4, Nikon being the best if you can afford it, with tamron, sigma and tokina all at the same level. non of them proform badly.
I believe all 3 mentioned lenses have a manual aperture ring, which is handy if using manual extension tubes, lenses like the sigma 150mm don't have a manual aperture ring so auto extension tubes would need to be used for easy aperture changing.