mps 430
I have experience with AVR,There are many peripherals in the AVR family like as ADC,comparator,REF,I2C,Dual USART, eeprom,Timers (with many featurs),LCD drivers.
There are AVR that have RF ,USB,secure,CAN Bus,FPGA,...
There are AVRs that are suitable for high speed and some for low power portable designs.
It have many support like as
www.avrfreaks.com and good documents on atmel site and internet.
It have some good c compilers from IAR , and free GCC.
freeRTOS also support it.
I think AVR does what you want in 8 bit and no need to learn others.
In next step 16 bit like as msp430 is not sufficient ,select 32bit ARM7 like as atmel
SAM7 series.
Msp430 does not have any new fearure.