I think the similarity between d20 and Coda, what there is, lies simply in the fact that there are some game concept designs that just work better than others, and games that are well-designed (which I define as "designed with an eye toward being fun to play" rather than "designed with an eye toward showing what a great designer the game has") use these. Coda is, from my first experience, a very intuitive system. It has a nice learning curve, and incorporates some ideas that make it really snazzy, like the wound levels and the advancements. It is not "different for the sake of being different". It takes classic RPG design elements, combines them with the best of the ideas from it's predecessor, and produces a smooth, very playable system that does exactly what it sets out to do.
My sincere thanks to all the designers of the system; this is the Star Trek game (and possibly the RPG system as a whole) that I've been waiting for :)
Allen