There isn't a single best if that's what you are looking for. With the wide range of uses for pcs, there's a wide range of different benchmarking software. 3dmark, pcmark, sysmark, sandra, cinebench, unigine, specapc and specviewperf, crystaldiskmark, iometer, luxmark are some that you will see in most pro reviews. Some of those are workstation and compute uses. Userbenchmark is probably the quickest and simplest to compare to others. There are also real world apps with standardized runs for handbrake, 7zip, photoshop, blender, etc. If you are looking at just games then you'd want to use the in game benchmark for the games that have them to get a real world idea. But again you are still looking at multiple benchmarks with the different needs of each game.