A laser rangefinder gives you the exact distance to whatever you point it at. Aim at the flag and you get the number to the flag rather than to the middle of the green, which is what makes it the more precise of the two distance tools.
What separates one rangefinder from another comes down to a few things worth knowing before you buy. Slope adjustment corrects the reading for uphill and downhill shots and switches off for tournament play. Magnification and maximum range decide how easily you can lock onto a distant target. A built in cart magnet keeps the unit on the frame instead of loose on the seat. Display type affects how readable the number is in bright sun.
A rangefinder needs a clear line of sight. If the green is blind, or you would rather have distances without aiming, a GPS watch or handheld is the other route. Those are in Golf GPS.
