1. Metric systems make most calculations easier, but not those including degrees of temperature. There is no advantage either way. There's always a constant expressed in degrees. So while there is a huge advantage to using kilograms over grains and Troy ounces, there is no advantage in Celsius over Fahrenheit for computation.

2. Both scales are 100 degree scales. Both are European. Celsius used 100 degrees between freezing and boiling, while Fahrenheit preferred the 100 degrees between the average coldest temperature Europe got to in winter and the hottest it got to in summer, where he lived.