If you've played Returns you will probably have noticed that the game feels more like an adventure game with a number of instanced point and click scenarios and some combat rather than a proper RPG. The pacing was awkward, there isn't much content, and story characters have little impact on anything, with the player mostly filling out the party with hirelings.
Dragonfall changes all that. Right from the start there is a full party of story characters running with the character you create and there's a much stronger story hook. The story characters stick around in the hideout and you can talk to them between runs, as the game advances you can unlock more dialogue with them and they all have backstories. There's also a full town hub which you can explore between runs, rather than just a single two-room building like in Returns.
There are also way better roleplaying options in missions themselves, better balance of skills and weapons, and the story is much more interesting in terms of how it ties in to the larger world lore of Shadowrun. More ambitious, and way better ending options based on your choices.
If you play the Director's Cut on PC, there's also a totally revamped UI, a new armor/cover system, more optional missions, and every single story party character has a character-centric mission which has two possible outcomes determining what special skill they get after it is completed.
