The only difference is storage & DVR!
If you plan on recording hundreds of hours favorite TV programs and downloading movies from the Internet to play back on your TV, then the Vulkano Blast is the best product for you. It comes bundled with a 160GB external hard disk drive that lets you record around 400, 90 minute TV shows and movies giving you the ultimate DVR experience.
If you feel you will only record 30 or so 90 minute TV and movie recordings, then the Vulkano Lava is perfect with its 4GB of Flash memory.
If your just looking for a great deal on some terrific technology that lets you watch TV on your mobile, then purchase the Vulkano Flow.
Here's a hint; buy the Vulkano Blast, once you experience DVR, you will record everything!