Some other things to think about with the 500 vs the 600.

You gain 20% of reach, for instance to get the same framing with the 500 at 100' you will be at 120' with the 600.

The 600mm weighs 22.9% more.

The 600mm mfd is 21.6% farther away.

At B&H the 600mm will cost you 27.7% more.

It might sound silly, but in all those areas you loose ground to gain the 20%.

MFD would be important if you were liked to take pictures of birds in the back yard where you can control the distance to your perch, or in the wild if you are able to get to the MFD. To me there I see no advantage to the 600mm, and to the contrary you the 500mm would be the better tool. Primarly because of Bokeh, if you are closer to the subject it increases the ratio that your background is from you and the lens can do a better job with the blurr.

Of course the 500mm is better for packing and carrying because of its size and weight.

With the 600mm in the field if you are shooting birds and you can not control distance, the 600mm rules over the 500mm.

So really I think it comes down to use, both are excellent lenses.
From my point of view it boils down to this.
If birds in the field are your thing the 600mm is the way to go.
If big game and general wildlife is your thing then I give the advantage to the 500mm.

But if I were you I would not buy either one. It is such a tough decision maybe you should wait for the 800mm II to come out .