Compact blocks, which are approximately 32kB in size for a block containing 4000 transactions, offer a more data-efficient method of transmitting block information compared to sending individual transaction inventory messages. The analysis suggests that with compact blocks, the breakeven point for efficiency compared to merkle proofs—used to validate the presence of transactions within a block without transmitting the entire block data—is around 80 transactions per block. This efficiency threshold indicates that for blocks with transaction counts above this level, compact blocks present a more bandwidth-conservative option.

The discussion extends into the realm of weak block transmissions, highlighting the redundancy and inefficiency of using INVs in such scenarios. Here, the challenge arises when a transaction is relayed to a miner's mempool but not to all peers, subsequently getting included in a weak block, and then necessitating another round of INVs for the same transactions. This process is significantly less efficient than using compact blocks, as each INV consumes more space (36 bytes per transaction) compared to the data footprint of a compact block (8 bytes per transaction). The suggestion to enhance INVs with merkle paths to target desirable transactions for rebroadcasting poses an additional challenge due to the increased complexity and codebase modifications required, making it a less appealing solution.

Furthermore, the potential savings of using compact block relay over enhanced INVs, estimated at 480kB per real block (considering weak blocks to be 1/16th the difficulty of real blocks), underscores the practicality and efficiency of compact blocks. This savings, coupled with the inherent complexity and additional coding effort required to modify INVs, strongly suggests that leveraging existing compact block relay mechanisms is preferable for optimizing block transmission within the blockchain network. This approach not only streamlines the process but also aligns with the goal of minimizing bandwidth usage and improving overall network efficiency.