Any chemists or biologists on here that can answer a few questions about calories?

If 1 person was to eat an excess of 1000 calories of fat, and another was to eat an excess of 1000 calories of sugar. Who would gain more weight? Does it even matter?

What is the process of converting ingested sugar into body fat and how efficient is it?

What is the process of converting ingested fat into body fat and how efficient is it?