Final answer:
Soho should use an Affiliate Marketing Platform to collaborate with bloggers, as it provides tools to manage and track performance-based partnerships effectively.
Step-by-step explanation:
The most suitable tool for Soho to use for collaborating with bloggers to post links to their blogs and showcase service testimonials would be an Affiliate Marketing Platform. These platforms are specifically designed to facilitate collaborations between advertisers/brands and content creators or publishers (in this case, bloggers). By using an affiliate marketing program, Soho could track the performance of these collaborations, manage commissions or rewards for bloggers who drive traffic or sales, and effectively engage in performance-based marketing.