Do you agree or disagree. Working more efficiently with existing vendors is better than Identifying new vendors?

Both. You build trust while working efficiently with existing vendor and you explore opportunities with identifying new vendor. As long as it's a win-win for both then having old and/or new vendor is always good to have for growing business.

i absolutely agree with clodelio delfino.

Generally speaking, yes. But it really depends on sector (service vs product) and your degree of dependence on your vendors’ availability, capacity or numbers.

Sometimes, your core business relies on relationship with vendors with very comparable products, services, prices & quality, but who differ in availability, delivery-time or location, for building a big network of vendors is more advisable than relying on a couple existing ones, as long as having a big vendors network remains cost-efficient.