Question: Whose mercy is more important, Guru or Krsna?
There is no difference between the mercy of Guru and Krsna, no difference whatsoever. The Guru is the direct representative of Krsna in each of our lives. In the beginning, we naturally see that the Guru is more accessible because he is here in our world and he speaks to us directly. Sometimes he would chastise us, and sometimes he would encourage us. So the Guru has the power to correct us.
Krsna on the other hand is silent. Now, He may be speaking to us, but we cannot hear Him. So in the beginning, we need the mercy of the Guru so that we can eventually obtain the mercy of Krsna. Ultimately however, both their mercy is the same. The mercy of the Guru is the same mercy that flows from Krsna. If Guru has any mercy, where does he get it from? Dharmam tu sakshad bhagavad pranitam (Srimad Bhagavatam 6.3.19) – The origin of all religious principles is Krsna. So whatever spiritual mercy that the Guru has, he has got it from Krsna. That mercy from Krsna is all he can give us.
Therefore, in the beginning, the mercy of the Guru is more important because it is the Guru who holds our hand, takes us to Krsna and then leaves us with Krsna so that we can eternally serve Him.