Puckman wrote in post #17533693
Is the Sony version significantly lighter than the canon equiv f4, not 2.8)?
If not, there's really no point.
It really depends on your needs. For me the three FE zooms are all about convenience; all about walk-around usage. In that type of usage I want that flexibility of the zoom and good AF performance. So, I would say that while there may not be a weight advantage for the Sony 70-200mm (don't forget to factor in the weight and extra length from the EF-to-E adapter!), it does enjoy a strong advantage - on the a7 series - in AF performance.
Also, as a former EF 70-200mm f/4L IS USM owner, I can say the OSS on the Sony is super quiet. The IS on the Canon used to drive me crazy.
But, again, it all depends on your usage needs. If you're mainly needing the lens for landscapes (especially with UWA zooms like the EF 16-35mm f/4L IS or EF 11-24mm f/4L) then AF may not be needed.
For me, the three FE zooms are my go-to lenses when I need the ultimate in flexibility - it's nice to be able to get excellent image quality from three lenses that cover a range from 16-200mm.
Primes are mainly about optimal image quality. For the most part I am a prime shooter. And even though I describe my FE zooms as my go-to walk-around lenses, I also frequently enjoy the creative challenge of picking up a prime and going out to capture images that suit that one focal length. It can lead to disappointment when you encounter a potentially amazing shot that doesn't fit the fixed focal length, but it also leads to a different sort of creativity where you might find great shots that you wouldn't have otherwise considered had you had zooms.
I like having both zooms that maximize flexibility, yet provide excellent image quality, and primes that maximize image quality and BOKEH!! 
