First priority range-finders are mainly used for the golf and in these there is nothing between you and the flag. Second priority rangefinders are generally hunting range-finders and it ignores the first object in its line of view and reads the object that is at the farthest distance.
This is undoubtedly the most confusing parameter while selecting a rangefinder because the product may mention 1500 yard range but that would only be under specific conditions like clear weather. When the weather is not clear, the results may be reduced. So you need to properly check the specifications before you buy a range-finder.
Reticles and aiming points:
A reticle is basically the crosshair that you see while looking through the range-finder. Some may be illuminated (LED lights) while some may be made of black lines. It is very difficult to distinguish the black reticles during dim light whereas the LED reticles do not work so well in bright conditions. So make your choice keeping the pros and cons of both. In general, the black reticle is better and is more capable view the information in different light conditions.
The other factors might be the cost, your budget, whether you are looking for quality or cost. You will surely find the one that you need. All you need to do is set the correct requirements list.