When it comes to choosing a scope for their rifle, snipers have two main options: FFP (first focal plane) or SFP (second focal plane). Both have their advantages and disadvantages, so it really comes down to personal preference as to which one is best.
FFP scopes are generally more expensive than SFP scopes, but they offer the advantage of being able to hold their zero better at different magnifications. This is because the reticle is etched onto the glass lens itself, so it scales with the image as you zoom in and out. This means that you can make accurate shots at any magnification, whereas with an SFP scope the reticle will appear to be in a different place relative to the target at different magnifications.
One downside of FFP scopes is that they can be harder to use in low light conditions due to the smaller field of view at higher magnifications. They also tend to have a shorter eye relief, which can be an issue for some shooters.
SFP scopes are less expensive than FFP scopes and offer a larger field of view at all magnifications. This makes them easier to use in low light conditions and they usually have longer eye relief too. However, because the reticle is not etched onto the glass lens, it will appear in a different place relative to the target when you zoom in and out. This means that you need to re-zero your rifle every time you change magnification settings if you want to maintain accuracy.