Chrome vs Stainless hubcaps?

[oem4me]

So, I'm going to be listing some hubcaps for sale soon, but first I'd like clarification on what I have. My truck interest/knowledge base is primarily with the 60-66 era, so I need a little help on these later caps.
Q: What is the deal on chrome vs stainless versions? I heard that a yellow bowtie meant '73 and later, but it seems logical to me that stainless would have replaced chrome over brass, so how is it that I have a chrome later cap, when I've seen stainless (with blue bowtie) earlier caps? Also are the chrome ones relatively rare? less or more desirable?

Below: First cap is original chrome, second is NOS stainless.