Latency of Serial.println() with Arduino UNO

As a part of my current experiment, I’m running following piece of code:

   if (digitalRead(pinDeviceReadReady) == HIGH) {
    Serial.println("DATA READY");
    spiSend(0x20); // command "read request"
    readBuffer.deviceId = spiReceive();
    Serial.println(readBuffer.deviceId);
    readBuffer.wireId = spiReceive();
    Serial.println(readBuffer.wireId);
    readBuffer.length = spiReceive();
    Serial.println(readBuffer.length);
    for (int i = 0; i <= readBuffer.length; ++i) {
       readBuffer.data[i] = spiReceive();
       Serial.println(readBuffer.data[i]);
    }
  }

where

inline void spiSend(uint8_t data)
{
  // wait for device ready to write
  while (digitalRead(pinDeviceWriteReady) == LOW);
  SPI.transfer(data);
}

inline uint8_t spiReceive()
{
  while (digitalRead(pinDeviceReadReady) == LOW);
  uint8_t data = SPI.transfer(0);
  return data;
}