Nevermind I just found your old post @kajfik000.
"50% Push the Limit becomes 18% in Arena, so it boosts your dmg by 18%.
Momentum(3) without any move speed affixes boosts your dmg by 30% of total MS bonus, so if you don't have any MS affixes your total MS bonus is 100% and Momentum boosts your dmg by 30% * 100% = 30%.
30% > 18% so Momentum affix is better than Push the Limit.
That is my reasoning why I use Momentum."