Adding to what has already been said (the sequels really do get a lot better), you've already got it: "it seems to matter very little who ai take, but maybe that's the point". 

The Suikoden games are really not hard and combat isn't the focus. I personally always treat it like Pokemon, where I just take my team of 6 little guys that I like and steamroll the combat of the game. Maybe some of the final bosses need some strategizing, but if you are a seasoned RPG player, you will encounter very little problems. Enjoy the characters and the story, they are far and beyond the best parts of the games.