There is no easy answer, because it all depends on how the small business was started, and the capital obligations of the business owner.
If it was bootstrapped and financed from growth, there is relatively low risk. But if one puts a substantial amount of cash into a startup or purchase, there is a lot of risk.
But on the whole, having done both for a number of years, I'd say there is less risk in trading because I have more direct control over the variables that can impact risk, and I don't need to rely on others to get things done.