Ridiculously compelling storytelling. I'd still recommend you watch Breaking Bad first, but this stands on its own and doesn't rely on its predecessor at all. It's very slow by comparison - by the end of the third season it's hard to pinpoint exactly what's happened so far. It steadily gathers momentum and each and every episode has been a delight to watch. I have yet to be disappointed by anything in this show; the strong acting and casting, the sets, costumes and props - everything is expertly crafted and it's all underpinned by truly gripping writing.
As a prequel to Breaking Bad it does a remarkable job of keeping us invested, even when we already know the fates of many of the characters. For instance, Jimmy and many others won't possibly die in Better Call Saul, because we know they already appear in Breaking Bad. It would be easy to assume that this awareness of the larger plot would ruin our experience, but in reality it just makes us question the other elements of the show that much harder, such as speculating why several characters may be absent from Breaking Bad. It's also framed within the flash-forward scenes of 'Gene', showing what happens after Breaking Bad, so there's still a sense of progress.
It's impossible to pick a favourite character when they all bring so much to the table. Bob Odenkirk continues to be an iconic ambulance-chasing "criminal" lawyer, but we see the additions of many new characters that feel as though they've always been a part of the greater story, like Kim Wexler (Rhea Seehorn), Ignacio Varga (Michael Mando) and Chuck McGill (Michael McKean). The addition of main character Lalo Salamanca has been wonderful as well and it's been a pleasure to revisit many of the background characters too.
If you've got the time to invest in all of Breaking Bad and Better Call Saul, I strongly recommend you do. If you don't have the time, make up some excuse and watch it anyway.