Darlene Conner or Leslie Winkle?

Hard to compare... one was a long-running central character to the Rosanne series, and the other was a recurring character that only made a handful of appearances, although memorable.

I also felt as if the Leslie Winkle character was an adult, more educated version of the Darlene character, with similar characteristics (sharp wit, sarcastic, etc.)

I will say that the episode with Leslie and Leonard were practicing their instruments made me laugh out loud and was hysterical, but I've seen that one much more recently than when Sara and Johnny played off of each other in Rosanne and think they had great chemistry there, as well.

Maybe Leslie... a lot of humor in a limited amount of face time?

Leslie Winkle

I'll say Darlene. She actually mattered in the Conner universe, while in Big Bang she was tossed in as a novelty, an amusing reference to their previous dalliance on Roseanne.
I've always been fascinated with her dry, observational style, her rejection of glamorous trappings.
She's not unattractive and she isn't trying too hard to be so, (attractive, that is).
Seems unusual in the current circumstances to not kowtow to wearing high heels, slim skirts and a ton of make-up.