Here are the main differences:
* Commanding is much less stressful. Giving the marines their own resources and the ability to buy their own weapons means you can focus more of your attention on just coordinating attacks and getting upgrades.
* Stalemates are much less common. In NS1 taking down the turret factory would mean that there's an opportunity for everyone to rush it to take the rest of the base, now every room has a power node in a fixed location that powers down all the structures when it is destroyed. This makes it much easier to force a beacon, and to end the game once the marines are down to their last base.
* Each class is much better balanced. Excellent Fades are no longer the sole backbone of a good team. Lerks now are useful at all skill levels. Exosuits are extremely powerful but very vulnerable when alone.
* Gorges are now a nice-to-have when building instead of absolutely necessary. This means they can be on the front-lines more often.
* Graphics (obviously) and very dynamic environments. The infestation spreading is beautiful, and taking the power down makes for some very tense moments.
