Is it better to hire licensed or unlicensed contractor?

[Jacky Johnson]

I'm planning on replacing all the sewer lines under my house from the sewer cleanout. I got two bids from two licensed contractors (plumbers) around $6500 and I think they are too expensive (I was thinking about $4000). Should I hire a unlicensed contractor hoping to get a lower price or should I get more bids from licensed contractors? What are the pros and cons of hiring licensed and unlicensed contractors in a long-term risk/benefit analysis? Or how should I handle this situation?

Thank you!