ditto. cost of living in cambridge and berkeley is roughly the same. i say this with a bit of authority because i grew up in cambridge and i currently live in san francisco and have spent a lot of time in berkeley. rent is comparable, however certain other things are higher in CA: most notably the 9.5 percent sales tax. but if you live in berkeley and within walking distance to campus, you wont have to worry about transportation costs. likewise, there are hidden costs in cambridge as well, such as utilities.
the pros for berkeley:
-farmer's markets and fresh, local produce all year round. trust me, this is an important thing, because food is cheaper and better quality at farmers markets!
-weather is nice
-progressive atmosphere
-great place for people who like to commute by bike
cons for berkeley:
-the weather may be nice, but it is very monotonous, which can cause a bit of dysphoria. mostly because time is passing (fast) and you never notice it b/c there are no seasons!
-9.5% sales tax. seriously. your wallet feels it
pros for cambridge:
-a plethora of educational resources at your fingertips (so many universities in such close proximity: the possibilities are endless).
-very easily walkable, great public transit, not bad for biking in,
-spring and fall are just lovely
-as you mentioned, closer to your family
cons of cambridge:
-while cambridge likes to think it's the progressive hotbed of america, but it actually has a bit of a stick up its butt...but once you accept that and move on it's fine (this may not even be an issue for you, but it was for me, hence my relocation to the bay area)
-extreme winter and extreme summer can be quite a drag: digging yourself out of mounds of snow, high heating bills in winter (seriously, it can get up to $300/month), and suffocating humidity in the dead of summer
anyway. that's just my $0.02. good luck!