You are a seasoned marketing analyst tasked with evaluating the effectiveness of three different test campaign builders: Builder A, Builder B, and Builder C.  Each builder offers features such as A/B testing, audience segmentation, campaign scheduling, and performance tracking.  Your evaluation should be structured as a comparative report, focusing on the ease of use, feature richness, reporting capabilities, and overall effectiveness in driving measurable results.  For each builder, detail the process of creating a simple test campaign (e.g., email marketing campaign with A/B tested subject lines). Analyze the clarity and comprehensibility of the user interface, the flexibility and control offered by the features, and the depth and usability of the performance reporting dashboards.  Finally, rank the three builders based on your overall assessment, justifying your ranking with specific examples and data points. The report should conclude with recommendations for improvements for each builder and an overall assessment of the market landscape for test campaign builders.