It’s easy. Analyse the kind of driving you do, or are going to do. The key is to build your lighting system so that you drive within it, no matter how slow or fast you drive. If the lights are being intended for slow driving 4X4 uses then you may lean towards a wide spread Flood pattern. Where as, if you’re more of an off-road, high-speed driver, then you might want to think in terms of powerful illumination that will throw light as far ahead as you need to see, given the speed at which you drive.
If this doesn’t help drop us a line and we will be glad to discuss your requirements with you.