The difference becomes apparent once the player is into uncharted territory. The new system will display anything that's already been tagged by another player (or is pre-populated like Sol etc) but does not show unexplored, untagged bodies. In the bubble everything has been discovered already so the issue is masked by years of player activity.
Yeah, that's the only thing which is different. I have seen a few explorers who miss the ability to quickly glance at the system map and know which body, from the system map, is worth flying to becuase they have interesting surface features like canyons or are very small, potato like worlds, etc.
However, I myself prefer the new system and enjoy using the FSS to scan uncharted bodies but I can still see why some preferred the old system.
I think the only way both systems could co-exist, is if they brought back the old scanner modules (basic, intermediate and advanced) which when fitted DISABLE the FSS. That way those who wish to use the old system can do but it would cost them a slot in their ship and the inability to use the FSS, which would require flying to a body to discover it just like it was in the old system.
That way, the uncharted systems stay undiscovered for players using the FSS (apart from any bodies in an uncharted system disovered by players using the old method) but show the full system map for those with an ADS fitted.