Those that attempt to measure specific performance, such as raw compute power or bandwidth of specific subsystems. Those that are only intended for marketing purposes or to mislead and deceive. Both Sysmark and Winstone attempt to give you a measurement of overall system performance. Raw computing power only plays a minor role. Overall throughput is the metric of choice.
Some benchmarks attempt to measure specific performance, like microprocessor and disk subsystems.
Benchmarks can also be devised for marketing purposes, and their published results should be carefully weighed. Therefore, the results couldn't be independently verified. In short, vendors know that peripherals make more difference in benchmark results than any motherboard design or CPU choice. Differences in motherboard design would never account for more than one or two percentage points of benchmark results. Likewise, whether you choose an AMD, Cyrix, Intel, or IDT 586-class CPU will not make much of a difference in most benchmark results either.