What is the best thing to do, smoke, chewing tobacco or snus if I had to choose?

Choose none. Interestingly, you do get to choose; choose none as all are bad for your health. No one is forcing you to choose only from the three.
Snus, I guess. But it's like asking - doctor, which is better? I could shoot myself in the head with a 45 caliber bullet, a 22 caliber bullet or just hit myself repeatedly over the head with a hammer. Well, in that case - pick the hammer. But how about - none of the above. All forms of tobacco increase risks of heart disease and head and neck (mouth) cancer. You are better off without any of them.