It's pretty simple. Chronically, if you don't die from an overdose->respiratory depression, than yes, there aren't a lot of negative health consequences involved when using Opioids. It has been said that, all things being equal (no dangerous substances in drugs, safe injection technique etc.), the most dangerous aspect of chronic Opioid use is the potential for gastrointestinal distress like severe constipation leading potentially to complications like toxic megacolon. There are options for reducing the risk of this sort of thing like, fiber in your diet, use of laxatives etc. The goal is just to stay ahead of the problem before it actually becomes a problem that you can't handle.
The primary active chemical in tobacco is Nicotine and Nicotine is a known carcinogen to humans. This means we know that it has a well-established propensity for causing cancers to parts of the body it comes into contact with. This could be the mouth and throat if using dip/chew, the sinuses and throat if using snuff and the mouth, throat and lungs if inhaling the Nicotine by way of cigarettes, cigars and even vaporizers. Vaporizers are arguably safer as their vapor does not contain the same level of tar and other harmful substances, but Nicotine itself will always be a carcinogen.
In short, Opioids are typically more dangerous in an acute setting, whereas Nicotine tends to cause harm mostly through chronic, sustained usage.
