Simming my own character on a patchwerk type fight:
489 Polearm: 80078
489 + 476 Fist weapons: 81712
= 2.04% upgrade
You might want to check this interesting article:
Level 90 DPS Rankings - Realistic Simulations (MoP 5.0.5)
Using a helter skelter type fight in simcraft gives the following value:
489 Polearm: 70323
489 + 476 Fist weapons: 70343
= 0.03% upgrade
Make your own conclusions

Or even better: run simcraft yourself, with your own gear