Saga frontier offered better music, a battle system with some flair, and a the same 50 characters that had no impact on story but were just plain badass (Lei-Fang, Liza, and Rouge for example, Gen had SOME story with T260-G). Suikoden 3 I remember Chris and the guy Geddoe I think, and the kid who's mother was a villian in part 2 were the main characters, and something about the true fire rune. 2 I remember the main character had tonfa, and his sister was annoying, and his best bud became a super dick. I played 2 less than a year ago, and I really remember nothing about it, other than the final boss pissing me off for a while, then I power leveled and came back and dominated it.
Basically, I don't like suikoden. Its battle system is boring and the music is terrible. The story is probably good, but forgettable, though I won't fault it for this, only a few games really stick in my head anymore these days. I will say outright I liked Saga Frontier much more than Suikoden as a series.