I thought it had those amazing "Boom" speakers. I was under the impression that it would be louder than anything else because of these front facing "Boom" speakers. Just hard for me to believe the One is not the loudest of any smartphone that has ever been created. They even say you don't need headphones because these speakers are so loud. I simply don't believe they are not the loudest of all smartphones.
I think "front facing" is the key. The OGPs speaker (singular) is rear-facing. It's capable of putting out a good volume, but being rear-facing all that sound is being projected away from you when you are playing a game or watching a video.
I found a measurable increase in volume by cupping my hand behind the phone, reflecting the sound back to me, instead of just having the speakers try to fill the whole room with sound.
So the One, for video/gaming/daily use, is probably going to have a "cleaner" sound even if the speakers were not technically superior, simply because you don't have to drive them as hard to get an acceptable volume.
The OGP's speaker seems more designed for speakerphone use, or possibly listening to music with the screen off, face-down.
Setting the phone down on its back muffles it a lot, and a case makes it worse.
I don't use the speakers on my OGP a lot, and I usually play any games and whatnot silent or with headphones, so this is not a real factor for me. But if one of your primary uses is to watch videos or listen to music, well, you'll have to decide between one of the largest and clearest and most drop-dead freaking GORGEOUS screens out there, or for about the same money a smaller screen with better speakers.