Back in the days of old when Linux was a relatively new idea, it wasn’t uncommon to be able to install and run your distribution from a floppy disk. A few years ago, the norm was a CD and of course, the next natural step was only ever going to be the DVD. Now, there is nothing wrong with any of those formats (well, apart from the floppy disk, in my opinion) and they all do their job well enough but from the experiences I’ve had over the years and the convenience involved with using a USB flash drive, to me, there’s no comparison or competition… I would always choose the USB drive.
With a bootable USB drive, there’s are just some many benefits; fast boot times, improved speed and performance over using normal discs, convenience that comes with the portability, the great addition of saving any settings and changes you make via the persistence feature, the fact you can boot up almost anywhere and on anyone’s computer, the sturdiness of a USB flash drive over that if a CD or DVD that can easily be scratched by the most careful of hands, as well as the fact that there is usually some additional space free to store documents, downloads, etc. plus, if you ever get sick of using Linux from your USB, you can repurpose it and just wipe it so it can be used as normal portable storage.