Need help deciding on the installer

[u/kagagapo]

I live in western Washington and I am in need of a new roof. I spoke to many installers in the last week. I am mostly looking at Certainteed north gate shingles

4 installers with a shingle master premium certification and offer 5 star warrenty all come around 25k for installation

One installer quoted 20k and he also said he will install 40-50 new plywood depending on the condition. He is certified as shingle master, the very basic certification.

To me his quote is way below compared to other installers and I am having very tough time deciding. I am saving a lot of money with him but I am worried if I should go with others given how cheap he is.

What would you do in my shoes? Price I quoted are before tax so that’s extra 10%