Which simulation tool you use depends on many things, including your application, task you wish to perform, your experience level with hydraulic systems, which other physical domains your simulation will include (mechanical, electrical, ...), if your application includes a control system, and your budget for software purchases.
A big distinction between Simscape and any other hydraulic simulation tool is that Simscape is fully integrated with MATLAB and Simulink. If you intend to use your hydraulic system model together with capabilities from MATLAB and Simulink, such as control design, optimization, hardware-in-the-loop testing, and post-processing, you will have a much more seamless workflow if you use Simscape.
Some engineering teams use detailed simulation tools for the design of hardware components, such as CFD tools to analyze flow within hydraulic valves or finite element tools to analyze stresses and strains in parts. Those tools are complementary to Simscape, which enables system level analysis and simulation. The system level model enables rapid iteration on the requirements so that the engineer working in the detailed tool has better starting parameters and can get the job done in fewer iterations. The results from the detailed tool can be used to tune the Simscape model.
From your one sentence description, I suspect Simscape would be the better choice for you.
--Steve
