Are you talking about the TOS-ified Defiant-class warships on pages 5
on the "older posts" on this blog?
That looks OK but it's a very literal backdate design. The shapes and proportions are TOO similar. All that was done was smoothing out the hull and swapping the bridge dome and nacelle front/rear ends.
Ian's looks more logical, like something Starfleet cobbled together to test the concept. It got used on the sidelines and in special circumstances. Eventually, it evolved into the DS9 Defiant as ship design and technology changed over the decades.