It's back to age old question, use what's best for your own brand/style of Photography, I have both now & I've run some side by side comparisons with the 200-400/400f/2.8 v2/300f/2.8 v2 & 200f/2, the Primes still at the same range (200/300/400) & same f/stop, in my opinion have slightly sharper IQ, But it's minimal.
My first view was that I might off load my 400f/2.8 v2 as I know that in my Wildlife Photography the 200-400 will be King & no way will I off load the 300 or the 200, but, I shoot a lot of dawn/dusk so the 300f/2.8 & 400f/2.8 still have their place, the decision becomes what to take what to leave Home, that becomes dependent on conditions.
The 200-400 is a pretty fine Lens, sharp, fast, zooms, but, it's f/4, just something you need to consider & work within.
I can see inside sporting events in particular, under lights, difficult lighting conditions, the f/2.8 anything will rule.