well, that's difficult, you can look at the specs and very clearly there are similar cards, but in practice it varies;
we could look at the PS3 vs a Geforce 7900, and even with the 7900 having clearly higher specs with the same architecture, it couldn't really match PS3 settings later on, running the same multiplatforms, because PC had moved on (unified shaders) the optimization was not there I guess...
with a 7870, I'm noticing GCN 1.0 losing performance on newer titles,
RX 550 (2016's GCN with 512SPs @ 1100MHz, 128bit GDDR5) and the R7 370 (2012's GCN with 1024SPs@985Mhz, 256bit GDDR5)
if you look at Fortnite 1080P high
https://www.techspot.com/article/1557-fortnite-benchmarks/