A laser can be a useful tool but it has a fairly specific niche.
A laser will remove the need to align the sights. Typically, in order to shoot accurately, you need to align the front and rear sights then focus on the front sight. With a laser you don’t need that alignment and you can maintain your focus on the target. This can be helpful if your eyesight won’t allow a front sight focus.
A laser will not replace the need for good trigger control or follow through. If you want accuracy you will still need good trigger control and follow through.
A laser will not help you actually identify a target. All the laser is doing is removing the need for sight alignment. In conditions of low light you will need a white light to actually identify the target. A weapon mounted light is the best answer.
A laser is not a deterrent. If you are under the impression that the sight of a laser on someone will make them suddenly run away and you are not prepared to use a firearm to defend yourself, do not purchase a gun. A can of OC (aka pepper spray) can be purchased for a fraction of the cost.
A laser will not replace the need to become proficient with iron sights. In sunlight a laser can be nearly impossible to see. Not to mention a laser can malfunction, the batteries can die, or the laser can become occluded.
Understand and know your offset at different distances. A rough definition of offset is the different in point-of-aim and point-of-impact; it’s usually discussed with respect to rifles. Take the pistol out and shoot it at different distances to know what yours is. If the laser is not adjustable for windage and elevation, don’t waste your money. See the pictures for a Glock 23 and Surefire X400. All of the rounds were fired free standing.
I decided on a Surefire X400 – combination light and laser – for my nightstand gun. This gives me the versatility to actually identify a target and focusing on a laser is easier than looking for a front sight when I’m woken up in the middle of the night; the front sight is still there if I automatically go to that.