movement speed cap on stat page is [50%]. that cap only count direct boost m.speed like legend affix m.speed, mythic stone flight and Dexterity from heroic. so basically u need 2 legend affix move speed. 1 flight and 20 dexterity to have 50% m.speed.the hidden value/Max cap for M.speed is 100%. that another 50% is for indirect boost like sprint skill, zealous talent, zealotry set affix, advanturer set affix eth~. those indirect need certain condition to active like using sprint skill. equip hammer, max hp above 75% loot gold eth eth.
If u ask me what better, i would say both. and if u ask what better to equip i would also equip both. lol. more multiplying more damage.