Better Call Saul will be both longer and shorter than parent show Breaking Bad, depending on how you look at it. Early on in the run of the Saul Goodman prequel, which centers on the spiral of frustrated Jimmy McGill into his future status of Albuquerque's prime criminal lawyer, it was assumed the show would never outrun Breaking Bad.
The rise and fall of Heisenberg, Vince Gilligan's zeitgeist-capturing opus aired on AMC for a total of fives seasons over six years (season 5 was split into two, slightly-shorter runs), taking Walter White from docile chemistry teacher to child-poisoning kingpin. So far, Better Call Saul is four seasons in, with season 5 expected sometime in 2020, but according to Gus Fring actor Giancarlo Esposito, there will be a total of six.
That would mean that Better Call Saul will be on the air for longer than Breaking Bad: it has six production seasons to its five. And, because of delays, the show will have been around for considerably longer. While Breaking Bad released a new set of episodes each year for six TV seasons, Better Call Saul is skipping 2019, meaning season 6 will air in 2021 at the earliest, seven TV seasons after it started in early 2015.
However, that's only comparing the two shows by time on the air, not episode count or total runtime. While Breaking Bad had fewer production seasons, it did have six release blocks due to splitting an extended season 5 into two runs of eight episodes. Due to that and each of seasons 2-4 being 13 episodes (season 1 was a shorter seven due to the 2008 writer's strike), that means Breaking Bad has a total of 62 episodes. Better Call Saul has only ten-episode seasons, which means even running for an official full six seasons, it will only have 60 episodes. And, as the pair have similar average episode lengths (between 45-50 minutes), that will surely hold true for runtime when all is said and done too.
It's all a bit skewed, with either is the longer show by a small margin depending on how you measure it (something that happens all the time with TV records, with long-running shows never matching episode count of shorter-lived but denser series). What it highlights is that comparing of Breaking Bad and Better Call Saul just by length does a disservice to two series which, despite being intrinsically linked in a narrative and geographical location, are entirely distinct and telling stories in unique ways.
This comparison will get more complex soon, with the planned Breaking Bad movie that reportedly follows Jesse Pinkman after the series finale but will feature the return of Walter White and more, likely via flashback. When Gilligan is finally done, there won't be just Breaking Bad and its spinoffs, but a whole universe to explore, no matter what's the biggest part.