Also of note is the fact that Starshatter features both a large space-based combat environment (which FS has solely) and room-based environments. More specifically, it has multiple spaces which can be active simultaneously. Thus, combat can be happening in multiple different regions at the same time while the player is engaging in his or her own mission.
Atmospheric missions are not all too impressive as far as flight sims go, and they are fairly rudimentary (which in itself doesn't make them bad). As of this time, planets really only have one "room" assigned to them so far as I can tell. Entry to system sectors, orbits, and planets are once more all room-based. Thus, one does not simply fly to a planet - they will hit a key to break orbit and then wind up in the planet's atmosphere (in a fashion similar to our beloved Derek Smart's approach); leaving the planet is as simple as hitting the burners and climbing to high enough of an altitude to enter orbit. Thus, unlike FS, I do not need to wait while a new portion of the mission is loaded - I'm already there.
There are a multitude of things which still must be determined about the engine. For the vanilla game, I believe the program is using realistic units and... semi-realistic physics to do the job, which is not bad. However, the visual scale is very similar to what was seen in BtRL, where though the units are normal, the physical scale of the objects in the engine are not. The best way to illustrate this is to look at a pair of fighters in formation. Your wingman is said to be 2km from you, yet he seemingly cannot be more than a few hundred meters! The problem is that the engine also displays the size of the ships in the reference lab; understanding where and how the engine processes units and displays sizes is among one of the first tasks which must be completed in the process of potentially enhancing the game's physics, etc. That, along with visual updates (which are already progressing, mostly thanks to rscaper) will assumedly be among the first updates to the software.