16bit vs 8bit MCU flash userage

Hi guys

I find that a 16bit mcu use the flash a lot faster than a 8bit muc. In my case, 4K flash is lot for a simple project if i use pic/avr, but because I am using a msp430, the code size is just over 6K, and I end up need to upgrade my 4K msp430 to a 8K msp430.

Are 16bits MCU use more flash? How about 32bit MCU??

Thanks guys