It depends. I do most of my headphone listening in bed before I go to sleep. For years, I used an iPod, and then I switched to my iPhone because I like the interface so much better. When I got my iPad, I switched to that for a while, because I thought it was cool seeing so much more information (and bigger album art) on screen. But I recently switched back to my iPhone, because the device is smaller, and my objective is to close my eyes and relax, not hold a big iPad. I have iTunes Match, so I have access to my entire music collection in either case. However, when I feel like watching music videos on YouTube, I use my iPad, because the screen is bigger.