How does ThumbDV compare to a DV Dongle? 

ThumbDV
FTDI FT230XS serial to USB converter
No CPU needed
DVSI AMBE3000 vocoder
Software: Dummy Repeater

http://www.dvsinc.com/products/a3000.htm

DVDongle
FTDI FT232RL serial to USB converter
Atmel AT91SAM7S256 ARM7 based CPU
DVSI AMBE2000 vocoder
Software: DVTool

http://www.dvdongle.com/DV_Dongle/Home.html