If you're making fairly standard apps that substitute largely for websites - eg, login screens, some data in lists, couple forms - then you will probably want to go with IB storyboards. For these types of apps, development speed is most essential and future changes are mostly just tweaking the UI a bit as a large part of the functionality of the app is just pulling data from web services or doing standard calculations and displaying the result. Storyboards will let you get a nice looking and fairly simple UI done very fast and allow for rapid UI changes.
However, if you are going to have 3+ devs working on your app because it's actually the basis for a business or is very complicated, storyboards cause a lot of merge problems. They're far harder to create automated test code for. Refactoring your app becomes an exercise in tracking down IBOutlets. The couple days you saved at the start with easy layout and transitions get eclipsed by the amount of time you spend fighting IB later for changes. Also, if you use code review tools and have a heavy peer review culture then storyboards are a particularly bad fit.
Honestly I believe most apps fit into the first option and storyboards are the way to go. 95%+ of the apps on the Apple Store are definitely in the first category, and there usually isn't a need to over engineer them.