Stockfish 7 for Windows comes with 3 64-bit binaries:
stockfish 7 x64 bmi2.exe
stockfish 7 x64 popcnt.exe
stockfish 7 x64.exe
All 3 of them work on my system. Which one gives the best performance?
I think in general, the 'best' is x64_bmi2, then x64_popcnt, then x64 and x32 is 'worst'. That said, if your processor doesn't support bmi2 it won't run, etc. So pick the best one that doesn't crash.
To confirm this I ran the benchmarks given above.
On my PC (nodes/sec): stockfish_32: 1380872 stockfish_64: 1764951 stockfish_64_popcnt: 1813557 stockfish_64_bmi2: 1886284