There will be several difference between those blockchain projects:
Application: The specific application or domain they are focusing on. Some blockchain projects are public basic blockchains, like Ethereum, you can develop your own applications on it with the support of smart contract. While others may focus on certain domain, such as entertainment, storage, finance etc.
Consensus Protocol: as mentioned by others as well, different blockchain projects may use different consensus protocols, such as: PoW, PoS, DPoS, BFT, DBFT etc. So many consensus protocols were proposed. Although, honestly speaking, for now, only PoW works well for a long time.
TPS: it's actually related with the 2nd point, consensus protocol can certainly affect the performance/TPS, however, block design, and technologies like sharding, lightning network can significantly affect the TPS as well. Specific technologies used to improve scalability can also differentiate those projects.
Smart Contract: programming languages used to develop smart contract, whether the contract is secure, whether the development environment is user friendly, those are also the factors that should be considered to differentiate the blockchain projects.
