The transaction speed of the blockchain is super critical for conducting arbitrage: Since you might have to execute cross-exchange transactions, the time it takes to validate such transitions on the blockchain could impact the efficacy of your arbitrage trading strategy. For instance, it takes 10 minutes to one hour to confirm transactions on the Bitcoin blockchain. In that time, the market might have moved against you. Therefore, arbitrageurs should stick to blockchains with high transaction speed; or those that are not susceptible to network congestion.
In summary, to conclude a profitable arbitrage transaction, speed is critical. Your trades must be executed as fast as possible, or the opportunity might be gone!