My opinion is
C5050
1. 5 megapixel
2. fast lens f1.8 that allow you to take low lighting
3. Black in color
4. Better build
5. Support 3 different type of media ( CF , SD and xD )
6. Bigger LCD
Overall : good for taking landscape and people portrait shots
C750
1. 10x zoom
2. Cheaper
3. Smaller and lighter
Overall : good for landscape and nature including animal and birds shots
so the choice is still depend on you .... both have good images quality