Tam: Cooler, more varied terrain, better views, can ride there from SF, can also access via ferry, lots of car traffic.
Diablo: Hotter, great views, can't ride there from SF, can access via train (BART), very little car traffic.
When @
datlas gets back to PA from his California vacation, his riding buddies will say - "Hey wow, did you do Diablo?", and then he could either say "
Hell yeah!" or "No, I did Mt. Tam... it has more varied terrain and is a little less hot."