sadly her loadouts in other modes a suck so Carla is better.
..her load-out in Resident Evil 4's Mercenaries mode was pretty beastly, seriously..her rifle is more reliable than Wesker's magnum, great for killing bosses. ^-^;
I do like default Ada's load-out in 6's Mercenaries mode, the crossbow is a pretty cool weapon, decent boss killer, and the Ammo Box 50 isn't all that bad, I just hate the long reload animation it has..and sure, she may not be as superior as Carla in terms of scoring, but runs where I play as Ada are never dull for me, I like the extra challenge. =]
..as a character, I love Ada, she's sexy, intelligent, conniving, and an overall bad-ass, but with a good heart, and very generous. I love how she decides to leave the shotgun there in the house for Leon to acquire, how sweet. ^___^;