You will need to check the lumens - i.e. how much light is thrown out. This does come with a warning. If you are looking at halogen or metal halide, it is non directional, meaning that you have light spilled and therefore 50 to 70% of light is wasted, shining 360 degrees whereas your LED is directed light.
We stock a Luceco, British General 50W Flood Light with 3000 Lumen with a Beam angle of 95 degrees. Its IP65, meaning it is really good at withstanding rain. It turns on straight away - no waiting for it to heat up like metal halide.
So how far will it light up? The light spreads. The best way to show that is with the following graphic which shows a 30 Watt and 50 Watt floodlight mounted at 5 meters with a recommended downward tilt angle of 45 degrees.