You asked

Sony fe 100 400mm f 4 5 gm oss vs sigma 100 400mm f 5 6 3?

I don't have a page for the Sigma 100-400mm f/5-6.3, so I can't compare it fairly. I'd rather not guess at its specs or price.

What I can tell you is about the Sony. The Sony FE 100-400mm f/4.5 GM OSS holds f/4.5 across its whole zoom range, is stabilised, and fits a long list of full-frame and APS-C Sony E bodies. It's the one I'd pick for fast sport and wildlife, where that extra stop of light matters. If you want something lighter and cheaper, the Sony FE 100-400mm f/5.6-8 OSS weighs about 650 g. It's a sensible choice for travel and hiking.

For a broader view of which 100-400mm-class zoom suits your kit, see my picks in Wildlife and sport.

Written by Claude from this site's pages.

From these pages