I thought the dynamic with Angel and his team was better.
There should actually almost be a third option for this poll: The Scoobies S1-3. If that was on the table, with Angel, Cordelia, Faith, Oz, Jenny and Wesley part of it, I would have voted that way. I thought the way the relationships were constructed and played out, and the way the show progressed through them, was the best television I've ever seen.
Both post S3, I'd going with Angel's team. I thought they had better and deeper characters as the show went along, and the development of all of them reached a great climax in S5, and the addition of Spike only helped that.
To me, AI, right from the beginning with Angel, Doyle and Cordy to the very end with Angel, Spike, Wes, Illyria, Gunn, Lorne and Harmony (give or take Lindsey) was much more like a family than post S3 Buffy. They seemed really, really close to one another, and they felt like they needed each other. It always felt like it was them against the world, and I really liked that. It was a cool metaphor for life in your 20's when you're out of school and out on your own for the first time. I thought they nailed that.
Now, I liked the Scoobies. But after S3, there weren't nearly as many arcs with the group dynamic that pulled me in the way Angel did. I wasn't into Riley, Anya annoyed me endlessly, Xander/Anya didn't do much for me, Giles role in the show evaporated (which I didn't like), and I liked Willow less and less each season until S7. And, have to say it, while I liked her, Tara never felt as close to the group as Oz did to me. I really feel like losing Angel and Oz so close together threw the entire dynamic out of whack and they didn't really recover. And more than anything, Buffy, from her relationships with Riley and Spike to just the general feel of her place, always felt...isolated a bit from everyone else than she did in the high school years. But then again, I love Buffy, and I love the high school years, so maybe I'm just a bit biased that way.