Well, it may not be true anymore, but for a while r6515 was largely agreed upon to be the overall fastest revision of Dolphin, regardless of functionality and compatibility. Since I just needed all the performance possible to run it, I wasn't worried about anything else.
Dolphin 5.0 CPU benchmark
CPU: Xeon E3-1246 v3 (4c/8t Haswell/Intel 4th gen) — core & cache @ 3.9GHz via multicore enhancement
GPU: Intel integrated HD Graphics P4600
RAM: 4x8GB Corsair Vengence @ DDR3-1600
OS: Linux Mint of some variety + [VM] Win7 SP1 x64
CPU: Xeon E3-1246 v3 (4c/8t Haswell/Intel 4th gen) — core & cache @ 3.9GHz via multicore enhancement
GPU: Intel integrated HD Graphics P4600
RAM: 4x8GB Corsair Vengence @ DDR3-1600
OS: Linux Mint of some variety + [VM] Win7 SP1 x64