We shouldn't concentrate on the GPU in this case - the CPU will most likely be way better than whatever revision of a ps4 can offer.
This right here is the kicker.
Nobody knows the CPU solutions for either. But we all know the current cpu's are bottlenecks. These could be the real tie breakers in regards to fps and open worlds.
GPU wise 4.23 vs 6 will be noticeable but really not by much more than this gen.
RAM wise they will also be closer than current gen.
CPU though, that could make for some interesting comparison.
If Neo goes jag+ and Scorpio goes zen, there could be some major differences performance wise, but price will favor Neo absolutely. If both stick with jag+, the bottlenecks will be there for both but the prices will stay low. If both go Zen, Neo might price itself over the market more than Scorpio, but the performance on both would be incredible.
I feel like the first is most probable, unless Sony really pulls some magic out of a hat.