I have flown both types in Africa.
Operationally and reliability fly C208.
Zambia gets hot and the C208 has a good air vent...which on a given day is a life saver.
PA-31 is OK... I appreciate its a twin but when you walk out to work in the morning the C 208 will put a smile on your face but the PA31 might make you wince.
PLus the C208 is much more versatile which means more work and its slower which means more hours.
Hope this helps.