I sided with Faendal because he just seemed like the more deserving guy.
You have Sven that does nothing but sleep and drink all day and hang out at the tavern to drink and sing all night. Doesn't do any real work around the town and lives at home with his mother.
Then you have Faendal. Who every time I see him walking around town he's hauling lumber in one direction or another, is a proficient enough archer to be qualified to teach other people. and has a place of his own... with plants outside so he is also a capable farmer.
Faendal to me is clearly the better man to champion for Camilla's affections in my book. Though they both are wrong for offering to stoop to the level of deception to 'seal the deal'. I didn't take that route my first character... I talked to Sven... thought he was a creep and told Camilla about the letter. But add in the fact that Sven's mother actually does his fighting for him since....
Spoiler She hires thugs to attack you if you help out Faendal over her son
... pretty much everything about that guy just screams CHUMP, to me.