Internet of Things (IoT) platforms have a great number of vulnerabilities which cyber-attackers can exploit. A possible solution largely contemplated in the state of the art is to make use of blockchain technology in any IoT system to enhance the security of the platform while improving other of its aspects. Although there are valuable benefits of the use of IoT platforms based on blockchain technology, it is worth studying the different alternatives between blockchain technologies, because all of them have their own limitations that are not suitable for every use case scenario. In this work, we listed a number of flaws that blockchain technology has in this respect. We have identified that, most of the flaws can be overcome by adapting the variants of this technology to the specific needs of the IoT platform. Every IoT system based on blockchain technology, should perform a systematic analysis of their needs, identifying what are the blockchain features sought for that scenario, to choose the solution that best meets the needs among the different blockchain technology alternatives.