The speaker on my iPhone 4S is by far the loudest speaker of any iPhone since the original and the iPad 2. I did see in the latest software update that Apple said they tweaked TV shows and movies to sound louder on the iPad one and two I think. I'm very curious if the iPad 3 will be louder. I had a really hard time listening to Netflix, HBO GO, and TV and movies on the iPad 2 even with volume maxed. Even though the speaker on iPad 2 looked much larger and probably was larger than the iPhone 4S it definitely did not sound louder.
iPad Has 4 to 6 times more bass punch
iPad Is 5 times louder than iPhone
iPad has 7 times better sound quality
iPhone only good at 10-60% volume after that it will sound distorted higher than 70%
iPhone even the XS Max doesn't have any bass feel at all
iPhone has much smaller speaker less room and slightly quitter
iPhone Sound Quality is much worst than iPads