Appreciable difference over the 70-300 vr

I'm contemplating adding a super zoom to my kit and possibly selling my 70-300 vr to help fund the purchase.  I'm considering the Sigma 50-500 with or without OS.  The Sigma 150-500 OS or possibly the Sigma (or Nikon) 80-400 OS.

I am really wondering however if I will see any appreciable difference with these lenses to justify the cost.   My Nikon lens is quite sharp all the way out to 300 so with a little cropping of the image in post, I am wondering if it's really necessary.

Any thoughts would be appreciated.

Thanks,

Reiid