Mine gets a lot louder than my iPad 3. I had not heard that the iPad 4 had new speakers.
Edit: I must retract my original statement above. The two sound different as the mini has two speakers and the iPad 3 has one. However, when I used an app called cleartune to generate a tone and another app called dBmeter to measure the sound pressure level, putting the speaker of one next to the microphone of the other, they show roughly the same sound level at max volume. So I think they are really the same in terms of loudness.