In comparison with writing a code, the simulink provides an easy to use graphical user interface (GUI), and doesn't require high programming skills. In addition, the review, and debugging of a simulink model is relatively easier. The accuracy of the modeling using the simulink is higher as the probability of erroneous construction of a model is lower.

"Simulink provides a set of predefined blocks that you can combine to create a detailed block diagram of your system".

simulink has blocks instead of coding you can so easier use blocks to create your modeling system, but its important to know that, at first working with simulink it seems really easy but simulink some internal difficulty which working with matlab coding is so easier for me.

consider that in coding we have (for) loop which it can iterate our codes which you don't have this in simulink. this is one of the difference between simulink and coding in matlab.

Simulink provides a set of predefined blocks that you can combine to create a block diagram of your system, but using codes you are free in choosing assumptions, control strategy and so on. I agree with Khezr Sanjani.

Sometimes simulink models can give erroneous results because of assumptions in hidden variables . Physical behaviour of the system provides the clue. MATLAB coding route should be tried to verify the results in new cases and matched with Simulink results