We have the 3.5 mm jack for plugging in headphones. (pocketberry.com)
Swap it in and plug your headphones into it (instead of using the 3.5 mm jack on top of the phone) and you'll instantly notice how things sound better. (androidcentral.com)
.5 mm jack in my eyes because it can do audio and accessories, not that we should have to choose. (goodereader.com)