Quick gear tech:
Lower gears have a higher numerical number, and vice versa. Below, for example, 4.56:1 gears will be lower than 4.10:1 gears.
Lower gears raise your overall rpms at any given speed. Therefore, you get better off the line power, but higher highway rpms. This can not only limit your top end speed, but also cause you to suck gas on the highway. Lower gears will also enable you to "crawl" easier and better, getting more power at low speeds for conquering obstacles.
The goal with gearing is to match your final drive ratio to your engine's powerband. You take into consideration not only diff gears, but tire size, tranny ratios, tcase ratios, driving style and conditions, and the engine's powerband. <in a nutshell.