Hi all. Had a look at the Sony 200-600 in a local shop yesterday...looks good. However, I'm still unsure (and somewhat confused) as to whether I'll buy Nikon or Sony in an effort to get better AF tracking for bif images. I'm even more confused now, as I have read and watched videos regarding the apparent sensor dust issue that Sony cameras have. I guess it would not be an issue if I have only one lens attached to the body (thinking A9+200-600)...but it appears it's a deal breaker for a lot of photographers. Thoughts?