So I spend about 2-3 hours a day sitting on a bus, and at the moment I spend that time either sleeping or arguing with people on the internet. So in an effort to be more productive, I'm buying a short scale bass and looking at ways to practice sans outlets. So far the two products I see get the most mention are the Vox Amplug and the irig/amplitube/iphone combo. Either will let me play along with songs while sitting on the bus. Both are around the same price. So does one offer a significant advantage over the other? Any other options I should explore?