In a nutshell, what do you think these MSP430s do that AVR does not? I see there are a bunch of options on Digikey but mostly they have the same peripherals, similar number of pins, similar amounts of flash and RAM, very slightly better clock speeds (up to 25Mhz instead of 20Mhz) than tiny/mega AVR (not including XMEGA AVR which compares even better than plain AVR at 32Mhz and additional peripherals such as DAC). I get they are 16 bit, but does that often matter? Anyway, what is the draw?