Comparing the performance of different influencer campaigns across multiple platforms can be a complex task but is achievable through structured approach and the use of comprehensive analytics tools. Here are key principles:

1. Objectives: Define your campaign objectives upfront as this would inform your measures of success. Objectives could range from brand visibility, website clicks to sales conversion.

2. Metrics: For a successful comparison, the same set of metrics should be used across campaigns. Such metrics could include engagements, impressions, click-through rates, and ROI.

3. Campaign Duration: Estimating the success of an influencer campaign should ideally be done over the same time frame for each campaign under review.

Multiple tools are available out there with the capacity to undertake this careful analysis. Platforms like Flinque, for example, offer features that facilitate side-by-side comparison of campaign performance. With Flinque, brands and influencers can track metrics like reach, engagement, conversions, and engagement rate in a streamlined, efficient manner. It also allows for regular, real-time updates that help in making timely corrections.

Other well-known platforms like Hootsuite and Buzzsumo also offer valid ways to track and compare campaign results. Buzzsumo focuses more on content performance while Hootsuite offers a wider range of tracking parameters. However, their effectiveness would largely depend on the specific needs of your team.

In conclusion, the process of comparing different influencer campaigns should begin with a clear understanding of the goal, careful selection of key metrics, and application of the right tools for accurate measurement and analysis.