The 70-200 II has taken the place of the 100-400L in my travel kit. But, I would like a longer lens for birding and wildlife. I do use the 2x TC and the optics are close to the current 100-400L.

I would be curious as to people's thoughts regarding upgrading to the 100-400 II vs the Sigma 150-600S, vs the Tamron 150-600 or saving for a big white.

I know a lot depends on the optics of the 100-400 II, if it takes a 1.4x tc. But after seeing the size and weight, I am thinking the extra size and weight of the sigma may be worth it.