How different is up for debate but most studies and personal experience puts pot on the safer side. I knew many athletes that smoked it but never tobacco. In any case, pot smokers inhale far less smoke. They inhale maybe 1-3 times and share a small pipe/cig with breaks. While a tobacco smoker typically smokes a big cig that contains far more plant matter (by weight) for 10-15 minutes constantly.
I can also tell you 100% that pot smoke stinks up homes far less and airs out far more quickly than tobacco smoke. I knew kids that would frequently smoke pot in the house 1-2 days before their parents came home from trips. Hell, even have parties where pot but no cigs were allowed. Everyone knows you could NEVER pull that off with tobacco.
A kid can only buy from the machines with a cannabis card. They buy tobacco and booze with fake/borrowed ID now. I do agree that the presence of a clerk would prevent really young kids from simply swiping a borrowed ID. As it is, these machines are a bad idea. They can allow 24/7 store sales or use biometrics at the machine. Thumb scanners or face recognition is cheap now.