Run into a problem with our songs

I'm not quite sure if this is the right Forum topic to post this in, so anyway here goes.

Im in a three piece punk band and the last couple of days we have been fiddling around with a metronome figuring out how fast we want our drum beats to be for the our songs, however, one of our songs has a drum beat intro that goes for about 20 seconds, then stops, then goes into another drumbeat for the rest of the song. Now heres the problem. The intro drum beat is not the same speed as the drum beat for the rest of the song, its not half as fast, as fast, or twice as fast. Its actually just a bit slower than the drumbeat for the rest of the song. Now our guitarist seems to think that if you use different drumbeat speeds throughout the song they need to be either twice as fast or twice as slow for example. He says they can't just be "a little bit slower". Is he correct in saying this?