75400 Chalk Line Reel 100’Orange 4x aluminum w/rubber grip USTAPE

75400 is a good choice if you prioritize a simple and affordable reel with a wider opening for easy refilling.
The 75450 might be a better fit if you need a heavy-duty line with better resistance to fraying and prefer a tighter seal to prevent chalk dust leaks, along with the potential benefit of a higher gear ratio for easier winding and unwinding.
Ultimately, the best choice for you depends on your specific needs and preferences. Consider factors like the type of line you need, how important easy refilling is for you, and whether you require a tight seal to prevent chalk dust leaks.