This study presents a comparative analysis of randomized testing algorithms, commonly known as fuzzers, with a specific emphasis on their effectiveness in catching bugs in Solidity smart contracts. We employ the non-parametric Mann-Whitney U-test to gauge performance, defined as the ``time to break invariants per mutant'', using altered versions of the widely-forked Uniswap v2 protocol. We conduct 30 tests, each with a maximum duration of 24 hours or 4,294,967,295 runs, and evaluate the speed at which the fuzzers Foundry and Echidna can breach any of the 22 protocol's invariant properties for each of the 12 mutants, created both with mutation testing tools and with manual bug injection methods. The research shows significant performance variabilities between runs for both Foundry and Echidna depending on the instances of mutated code. Our analysis indicates that Foundry was able to break invariants faster in 9 out of 12 tests, while Echidna in 1 out of 12 tests, and in the remaining 2 tests, the difference in performance between the two fuzzers was not statistically significant. The paper concludes by emphasizing the necessity for further research to incorporate additional fuzzers and real-world bugs, and paves ground for further developments of more precise and rigorous evaluations of fuzzer effectiveness.