Tristate Buffer and Open Drain

Hi

I would like to implement open drain function with the verilog code below:

assign q = sel ? 1'bz : 1'b0; //open drain

assign q = sel ? 1'b1 : 1'bz; // use tristate buffer to model open drain function with weak pull up resistor

Both using Pin Assignment with weak pull up resistor on q.

So, are they equivalent? Will the tristate buffer cause the contention?

Thanks.