How do you define best? Lowest price rarely means best-in customer service or product quality. To me, best is defined as a company that designs creative promotions that meet your specific marketing objectives. In this case, you need more than an order taker; you need a promotional consultant that works with you to understand your business, customers, branding objectives, etc.
First, I recommend asking your professional network for referrals. Additionally, each year Promotional Products Association International (PPAI) Pyramid Awards honors the top promotions based on creativity, product usage, ROI, etc. To see the list of winners:
When evaluating any promotional products distributor, look at the company's website. Is it simply a shopping sites or does it offer value-added services? Are there case histories that illustrate expertise and creativity? Has the company won any awards? Is there a blog that demonstrates knowledge base? With the answers to these questions, you'll quickly be able to separate the true marketers from the basic product salespeople.