product development is the winner in my opinion. product architect sounds strange because architecture is immediately associated with buildings. It works for “systems architect” and similar things because a computer system is something you are “inside” when you use it, at least mentally.
product design would be ok, except that the word design has been cheapened for years now. many 2 year community college CAD courses call themselves drafting/design programs. every kid in a high school art class wants to be a “designer”. indeed, most of them already are, based on the logo sketches in the back of their social studies notebook and the b&w pictures they took of their buddies skateboarding. I’m not sure if “design” even means anything, actually. I can’t really think of a definition for it.
Also i feel design has a connotation of the frivolous, impractical side of things. All of the butterfly shaped, holographic cell phones and levitating kitchen robots on coroflot. the goofy vinyl dolls for grown ups, and the $1000 skull shaped hipster lamps. marc newsom’s groundbreaking blob of a doorstop, and furniture that will never be sat on. all of these are known as “design”. remember the “designer colors” of the early 90’s?
product developer has a much more professional feel to it, of someone who works with marketers, consumers, engineers, modelmakers and artists to pull together a completed product. An “industrial designer” takes a grey box from engineering, makes it black, and adds some chrome trim. A “product developer” figures out what consumers want, why they want it, and works with a diverse team of proffesionals to fill the need, make it work, make it cost effective, and make it look good.