You compare them by similarites, differences and stronger aruments.
!. Both agree that animals are sentient , have feelings and can feel pain
1. Both agree animals have rights
2. Both agree that animals must not be mistreated
3. Both agree that humans have a higher value as compared to animals
Singer gives 3 different reasons why animals should not be mistreated
1. They are sentient beings with feeling
2. They can feel pain
3. Mistreatment reflects badly on humans who are supposed to be on a higher moral plain
Regan agrees with the first two points but adds intrinsic value to animals similar to humans. Unfortunately he then contradicts himself by saying that animals have less value than humans because their have less thoughts or hopes or expectations of the future than humans.Intrinsic value should be the same for both.
Singer is more consistent, more utilitarian (you can eat animals) and is more like common sense .