Comparison of RSA vs elliptical keys

[Mark]

I'm trying to understand the differences in strength between an RSA key
and an elliptical one such ed25519 with cv25519. I know with RSA it is
pretty easy to "gauge" the strength 1024 vs 2048 vs 4096. 

I could not really find anything to say how strong these elliptical keys
are and how they compare to RSA ones. 


Thanks