How were mass killings in Bosnia and in Darfur handled differently by the global community?

Both should have demanded attention.

Bosnia is in Europe and was played out under the watch of European UN soldiers. It was also heavily reported on from day one by the European press, shortly followed by the US press.
Bosnia is only across (a very small) sea from Italy so can't be ignored.
Bosnia is a mineral rich country particularly in Iron, so therefore has some commercial value.

Darfur is poor, it's oil controlled by the North (at the time), and in Africa. It has an African Nations peace keeping force in lieu of the UN. When the UN did go in it was small scale and primarily African nations again. It was only much later that E Western UN soldiers were deployed in any significant numbers and mainly as observers.

In short the global community didn't know anything about Darfur and no one in power seemed to really care with the US going as far as denying the blatant genocide.
The mass murders in the Baltic war were being seen in peoples living rooms on the 10 o'clock news and European soldiers were deployed so people had a stake in what was happening.

Therefore the UN after initially stalling got it's act together in Europe to actively police the situation and then actively hunt down and prosecute those (from all sides) guilty of crimes against humanity. This was actively backed and followed by the global community who said lessons had been learned (again).

In Darfur little to nothing was initially done and when it was acknowledged they favoured sanctions which would be entirely ineffective when the Chinese have a massive stake in the oil. The global community was not well informed and therefore had more pressing matters. It also doesn't help that more and more people look at Africa and think " It's Africa this stuff always happens, we have our own problems".
Also the global community had no real stake in what was going on in a globally unimportant poor desert in Africa. It was only after relentless campaigning, some help from big name stars (George Clooney...) and some horrific news footage and stories that anyone took notice at all.
It took a long time to broker a peace and a new North and South Sudan but then the global community upped sticks and went home. There was and is no interest in going after the Sudanese leaders or the Janjaweed militiamen. There is no real interest in going back and policing the conflict that followed and is still ongoing.
This is in the main historical fact, although some is my opinion. With the will of western governments and money and manpower conflicts can be ended (The Baltic war and Kosovo). When there is no real will to intervene long term then you have the current situation in South Sudan.