Probably Lou, closely followed by Pat. Saying that, I voted for Pat simply because I've always considered her the ultimate 'go-to' woman. Peggy and Pauline were, indeed, formidable women, but they were very much concerned with their own families and those who may earn the privilege of being welcomed into the fold.
Pat was there for everybody; and she never judged and she never shamed. That's what made Pat so brilliant and gave her such a unique position in the show's hierarchy - she'd been there, done that and got the T-Shirt, and she wasn't about to shame anybody else for doing the same. Offer some stern words of advice and tell a few home-truths; sure, but she'd have your interests at heart. She was always looking out for you, not looking down on you, and she'd never get on her high-horse because she knew damn well she didn't have one to get up on. That's why Pat is the ultimate matriarch for me, because she wasn't just the matriarch for her clan or those close to her; she was there for everybody.