Prototype was more of a Teaser. Their only point was to draw comparison. "If Saber was a Dude, this is what it would have been like." The creators felt that this scenario didn't feel right, and so decided to change it.
Parallel stories in general are always fun. This is exactly why I became a huge fan of Visual Novels. They're basically Animes with a more "Manga-like" feels, as you're reading through most of it rather than watching animated motion.
However in a Visual Novel you are given choices through the course of the story. To pick this event or that event which end up resulting in different endings depending on the choices.
Sad to say that vast majority are geared for males and feature Sex as the motive to wanting to play. But, I have gone through a number of them and find that many have very fascinating stories with or without the "Hentai" moments. (Fate/Stay Night started its routes as a Visual novel "Hentai", but later graduated away from the Hentai and simply became a Visual Novel/ Fighting game.)
I would stop watching anime all together if we started to see more of these become Dubbed, and/or simply created in America. I try to imagine how famous Films would turn out if the audience had the choice to pick the character's choices.
The only problem I had with the Prototype Saber was, he had no emotions to speak of. At least with Emiya's Heroic Figure *aka Archer he had a lot of character built into him. Both making him feel likeable and a Prick at the same time. Seriously, he was a bad guy with serious style in Unlimited Bladeworks. Half the time you didn't know whether to root for him or want to kill him. That shows a good character.
Ay, los detalles en sus armaduras son geniales, también me gustan mucho sus dos versiones. También lancer de Zero y Archer de Fate normal. XDDD La verdad es que son todos son personajes de Type Moon son muy originales, a mi me encnatan.