I have the lighter with the double USB adapter. Why limit your options, especially on something that cheap. I've gone on trips already where I've forgotten my phone charger. I can get a lighter charger at a gas station. In fact, the one I bought on the last trip is now my F6B charger. I can't always get a USB charger cable.

The funny part is I tried to order the MP3 double USB, but they were back ordered, so I bought the cheaper lighter plug and USB adapter instead, and I'm very glad it worked out that way.