I have yet to attend Ad Tech, but I plan on going to the SF meeting in April. As for Pub Con, last time I attended was 2009, so my review may not be as relevant as those who attended in 2010.
Overall the event was well organized, keynotes were strong, Matt Cutts did a great job. Guy Kawasaki was there too, wasn't that interested in seeing him, but his presentation wasn't half bad.
Also, the classrooms were great for making connections because they were quite small, which proved to be great for having the chance to talk to the speakers after their presentations (my favorite part of any conference).
Bad points: Large amounts of speakers just... didn't show up. There were a bunch of technical difficulties, mic problems etc., I felt like I was in a college lecture hall with a baffled new teacher again fumbling as an a/v assistant rushed to their aid. However, the small rooms that I mentioned before made it so the mics really weren't needed.
Hope this helps. After talking to many people, I have come to the conclusion that Ad Tech is a better overall value.