Leliana, because well, she is a trained assassin, Varric is a total rogue. While he parries with his wit and humor, while throwing bolts with Bianca, he would prefer to stay in the back ranks. Then there is this, he would let Leiliana win in a close fighting match, because he is a gentleman and the fact she scares him a little bit.
I have to say Leliana, even though Varric is very smart, cunning and an expert marksman. Leliana is an expert assasin, kinda like Zevran. She has the close range advantage for sure, but if Varric were to spot her from a distance she would be dead meat. Tough!
Oooof, that's a tough one. Lelianna seems to have solid skills when it comes to wielding weapons. Varric says Bianca does the job for him, but I don't believe him one bit. He's a solid marksmen. If Lelianna used her stealth and got in close, she could give Varric a hard time. Varric has a lot of wit and cleverness, though, so he'd set traps or find a way to detect her. Thinking on all that, in a fight, I still think Leliana would win.
In a game of wits, though, I think Varric has her beat. >u>