At sector level, when clicking on a system, we access to a lot of information on the system that are not present at system level.
Some of that information (if not all) should be available at system level. To get to that information, we have to go back to sector level, check it, then return to system level. You don't access it while going to system level as you directly open the star map at system level (as it was the last viewed level before starting a mission).
Moreover, the button to return back to sector level should be more visible. It's too easy to forget there is an upper level to access other systems the way it is now.
By the way, small bug with the star map: if you return to bridge just before starting a mission (on the page with a view of the destination and the briefing) then go back to the star map, you're still on the page with the view of the planet but there is no briefing so you can't start the mission and the only option is to return to system level view.
Reconnecting directly to system level view would be better, I believe.
Anyone can feel free to use the thread to bring suggestions and discussions about the start map. ;)