Actually, both have their own best functions. It’s just that a one-way car alarm only sends a one-way signal from the key fob to the alarm. This is usually basic enough to arm or disarm remotes for lights and sirens.
Whereas for two ways, it sends a signal from the key fob to the alarm, then also sends data back from the vehicle to the user. Well, from here, you can know the difference. In our opinion, both are good, just adjust them to your needs.