You can use both simulink as well as simscape, its totally up to your choice.
Just providing some key differences between simulink and simscape
1:- Simscape is a part of Simulink.Simulink is a graphical programming environment for modelling ,simulating and analysis of dynamic systems where as simscape is a Physical modelling part in simulink environment.
2:- The signal flow in simulink is unidirection and in simscape the signal flow is bi-directional between blocks.
3 There is a source code provided for each block in simscape , you can make changes in that code to make your own custom block also in simscape there is a language called Simscape programming language to design new custom blocks,you can refer to this link Simscape language