Multi-cloud computing is getting a momentum as it offers various advantages, including vendor lock-in avoidance, better client proximity and application performance improvement. As such, various multi-cloud platforms have been developed, each with its own strengths and limitations. This paper aims at comparing all these platforms to unveil the best one as well as ease the selection of the right platform based on the user requirements and preferences. Further, it identifies the current gaps in the platforms to be covered so as to enable the full potential of multi-cloud computing. Finally, it draws directions for further research.