LSF Revan - The DS Mode, granted, does better than ep 3 in showing just what DS means. Let's NOT cut away when the kid gets slaughtered. You picked the option, deal with it. Also, over half your party winds up dead.
Still, LS has a better story and stronger character arcs. The crew are moral, honorable, and strong folk with lines they refuse to cross. Even the "DS" Canderous is operating from a strict code of morality and honor. HK is the exception, and he's just built for gleeful malice. The ending is an homage to where it all began - Episode 4 - and there's this sense of things coming full circle. From hero to villian, and working your way back with the help of good people.
Female, I include for other reasons. There were quite a few things on that game that were just not present if you played male, and the Bastila romance didn't do much for me.
DSM Exile - With the exception of Kreia, who stands ground no matter what alignment you choose, Exile's crew were wavering and easily led with a dangerous and exploitable vulnerability (untapped FS). All the better to play someone loading up the one-way bus to hell and taking on as many passengers as possible. K2 was, in every way, a darker and nihilistic game. Nothing you did really mattered - it all came to the same place. Unlike the repentant LS Revan, a DS Exile could have did what he did and had zero remorse...later turning to pride, taking down the other two. The cut content tends to point further to this - with Atton fighting Mical (female) or Brianna fighting Visas (male).
Male? What cinched it was Kreia's world-class creepy line comparing the "virtues" of the women aboard, Atris's barely restrained jealousy, and the Handmaiden. Brianna gets the closest thing anyone on that game gets to a full, demonstrated character arc. She goes from the shunned, "least" of the sisters into the one who is able to defeat them all.