At least in theory, both UNPROFOR forces were changed with the same mission, presumably with the same or similar command structure, and comparable rules of engagement.
Why were Canadians willing to stand between two fighting sides and engage in whole night of heavy combat, exhibiting high level of combat performance (0 dead on UNPROFOR side, 27 KIA on Croat side) while the Dutchbat was not willing or able to protect civilians?
I can answer this question as it pertains to my regiment, the PPCLI.
The answer is that the UNPROFOR orders to 2PPCLI, the Canadian unit at Medak, were to withdraw and stand down. The only reason the Canadians were able to partially deter the Croation ethnic cleansing was because they directly disobeyed UNPROFOR orders to withdraw and instead the 2nd Battalion CO ordered 2PPCLI to stand and fight, resulting in the Battle of Medak Pocket.
It may be noted that the French battalion, not under the direct command of the Canadian CO, obeyed UNPROFOR orders at Medak and withdrew from the area.