Technology is evolving exponentially, and researchers are seeking solutions to answer questions related to the benefits of using advanced IoT cloud computing platforms. There is a tremendous amount of research activity regarding cyberattacks on Internet of Things (IoT) devices. IoT ecosystems consist of physical objects or devices that interact with the environment, extract data, and communicate with a higher authority such as a cloud. Many IoT users are unaware of the underlying platforms that facilitate data collection. These platforms are also known as middleware, sit between the connectivity and application layers. There are more than 1000 IoT platforms on the market today, where many are open-source or commercial and provide services that include a device, data, and connection management. This paper presents a comparative analysis of some commercial and open-source IoT platforms such as Arm Pelion, Microsoft Azure cloud, ThingWorx, FIWARE, and ThingSpeak. We compare system architecture, management schemes, protocols, interoperability, and security. We used experimentation with real-world Internet of Things devices for the comparative study. We proposed a novel design architecture of a fully secure testbed that integrates critical components of an IoT platform. Hopefully, this study will motivate manufacturers to provide a better quality of service to help customers select the best IoT platform for their needs.