If I were going to have only one M-camera and had to choose between the two, I'd go for the M6. Wider VF, a meter and fewer miles on on the shutter. Also, there are affordable winders for an M6 -- not so much for an M2. An M2 is a 50-60 year old camera. They are beautiful and have proved durable, but when I had to choose late last year between selling my M2 and and one of two M6's, I sold the M2. Will I buy another some day? I hope to. But for my style of photography an M6 made more sense. Plus my oldest M6 was only 20 years old and still a baby in Leica M terms. ;-)
By the way, used to live by Lake Merritt. Rockridge has its charms though. Oakland is a great town.