I don't know. I felt Roche and Iorveth are quite similar, it's just that one is a human and another is an elf.

Iorveth's side of the chapter 2 is better developed. The production quality is higher. Army camp is meh. I first sided with Roche and was slightly disappointed in the story, though I liked asshole-Henselt character a lot: a real king. :) Sile had nothing to say, which was pretty sad. And I didn't like the 'friends' dialogs in the Henselt camp. In the Vergen your friends are way more intertwined in the story than in the Army camp.

On the good side choosing a different path is like playing a different game... awesome. Never ever enjoyed a second playthrough that much.