This is great question.
Simulink vs. Gazebo:
Simulink is a graphical environment for designing, simulating, and testing systems. With Simscape on top of Simulink, you can do a physical modeling and simulation of your robotics systems. By combing Robotics Toolbox and Navigation Toolbox features (and many other like Deep Learning, etc), you can add autonomy to empower your robot applications for air, ground, and sea. I think this answers your second question. Although Simulink with other MathWorks tool chains can do sensor-rich scenario and environment simulation, Gazebo supports many sensor models and physics engines for broad robot applications.
Simulink<->ROS<->Gazebo vs. Everything Simulink:
(MATLAB &) Simulink has a direct interface to Gazebo with and without ROS for robot simulation for those who want to use Gazebo. Since MATLAB & Simulink has a lot of tools for robot modeling and control, you can develop your robot algorithms and even robot applications and validate it with Gazebo simulator. Using ROS Toolbox, you can do a live desktop simulation of MATLAB/Simulink <->Gazebo. Gazobo can be replaced with a real hardware for HIL. Later, you can generate C/C++ codes and deploy it to your target embedded system.
Beyond this Gazebo, we support Unreal Engine for photo-realistic simulation as well for various application, such as Automated Driving and UAV applications.
If you want to know more, please let me know for setting up a call. Thanks.
