Sony A7Riii or 70-200mm f2.8 GM

[Precision Division]

I already have a Sony A9ii + 200-600mm lens, i can't decide between a second hand A7Riii or a second hand/new 70-200mm lens, i have just sold my Nikon 70-200 f2.8E and would like a Sony equivalent lens i can use with my A9 instead of dragging the 200-600 everywhere, also i quite like the idea of 42MP from the A7Riii, would love to here peoples thoughts on which they would pick and why if through personal ownership experience or wishes, cheers.