Not always lighter weight. Generally the damping system (compression and rebound) is more suited to the riding style you select. On xc forks it is stiff at the top becoming, in theory, soft once you get past the first few inches. This would allow the fork to react to bumps but not react to peddle bobbing. On fr and dh forks we use a lot of sag. The fork needs to ramp up suitably to take a bit hit while also being active enough to take VERY fast bumps.

Being able to adjust those (rebound, compression, especially high and low speed and preload) allow perfect tuning of the fork for the rider. With cheaper forks you don't get very much of a damping system. Usually a small hole in the pumping rod, spring and some oil. All adjustments are done with oil and wrenches and for the really skilled, a small drill bit.

For the bigger forks you also get stiffer. My z150 is stiff, my 66rc is beasty next to it. My old monster T made my 66 look like a pinner fork. Xc forks tend to get light, Ti materials, minimizing weight for better xc performance. a 3in quality xc fork will feel as good as a 4 to 5 in crap fork. Quality suspension vs quantity

Now do you need a better fork. I don't know, do you notice a weakness in your fork. Are you going fast enough to notice its poor damping, are you going big enough to bottom the fork out while still needing the fork to be active. Do you need a fork that weighs 2pnds less than your current model. Does the fork flex if you hit a technical section. If you answered NO to any of these questions, than stick with what you have. I only upgraded when I could see my fork flexing. It would twist and shout all the way down the trail. I sold my exr really quickly and paid for something more suitable.