Haven't tried Maverick for brunch, but I've been to both for dinner and I like Bar Tartine better.
Brunch/lunch last Saturday at Bar Tartine was fantastic, starting with a beautiful spring pea soup accented with a hint of mint (no cream), a rhubarb prosecco drink, nice loose-leaf tea (though I hated the tea infusing equipment), and an open face pork belly sandwich that was so good I ate almost all of it, thus throwing my digestion off for days. Nothing we had was a clunker, and I can't even really find a single fault with our food--it was just absolutely delicious, fresh, slightly inventive, and beautifully presented.
Opentable didn't list any available tables for lunch on Saturday, but I called anyway and they said to come on in. When we arrived around noon the restaurant was at least half empty, so I heartily recommend Bar Tartine for Saturday lunch over many more crowded and less delicious options.
While we we eating, a guy came in with a ton of shopping from the Ferry Plaza farmer's market--food doesn't get much more seasonal or fresh than what they're doing at Bar Tartine.
561 Valencia Street, San Francisco, CA 94110
Many like Bar Tartine, and I think Maverick is great for brunch. Are you looking for a more upscale place? If a more ordinary atmosphere will do (nice but not fancy), I think Chow has the best breakfast in the area. Canteen #1, Chow #2 for me. More upscale and later in the day, I like Maverick and Foreign Cinema. Intend to give Bar Tartine another try.