Why is there a difference in output when using Event Control Statement and Delay statement for a simple D Flipflop?

Question

I have created a testbench for a simple positive edge triggered d flip flop with synchronous active-low reset. In the testbench, the first case gives inputs at @(posedge clk), and in the second case, I am giving inputs based on #10ns statements.

In the first case, the output of the flop changes after 1 clock cycle, whereas in the second case, it changes immediately in the same clock cycle in the simulator.

Why?

I am simulating in the Quartus Simulator.

Code:

initial
begin
    //Case 1: Using Event Based statements
    n_reset = 1'b0;
    reset = 1'b1;
    d = 1'b0;
    repeat(2)@(posedge clk);
    n_reset = 1'b1;
    repeat(2)@(posedge clk);
    d = 1'b1;
    @(posedge clk);
    d = 1'b0;
    @(posedge clk);
    d = 1'b1;
    
    //Case 2: Using wait Statement
    #50ns;
    n_reset = 1'b0;
    reset = 1'b1;
    d = 1'b0;
    #50ns;
    n_reset = 1'b1;
    #20ns;
    d = 1'b1;
    #10ns;
    d = 1'b0;
    #10ns;
    d = 1'b1;
    #50ns;
    
end

Answer 1

Using wait Statement:

Delays the execution of a procedural statement by specific simulation time.

"#<_time> <_statement>;"

Using Event Based statements:

Delays execution of the next statement until the specified transition on a signal.

@ (< posedge >|< negedge > signal) < statement >;

Level-Sensitive Even Controls ( Wait statements ):

Delays execution of the next statement until < expression > evaluates to true

wait (< expression >) < statement >;

Now I think you are able to differentiate, Right?