Quality that is described and checked
ISO 9001 is about a company having fixed procedures for how tasks are planned, carried out and checked. For a client it means quality does not depend on who happens to stand at the machine that day.
Environment managed in daily work
ISO 14001 is about the company knowing its environmental impact and working systematically to limit it, for example in choice of materials, waste handling and energy use. It matters when your project has sustainability requirements.
What certifications do not replace
A certification is not a guarantee that a single product meets your requirements. Always ask for documentation for the specific solution, for example data sheets and marking where required.
Use the certifications as an indicator of how the supplier works and as a basis for dialogue.
Questions to ask a supplier
Who issued the certification, and does it cover the production that delivers to you? How are deviations and complaints handled? And which documentation comes with the delivery?