I've taken a few photography classes back in the day, so I'm pretty confident in my abilities with a DSLR, but my iPhone is a completely different story. Lighting makes all the difference, so unless you're outdoors in the sun, it's hard to take a good snapshot with a mobile.
You have way more control with a DSLR, and in low light situations, you can always turn to your trusty external flash. Yes, the iPhone has a built-in LED flash, but it's just not the same as a high-speed xenon. You almost always get an overexposed image. There have been some iOS apps that help you connect external flashes... more