Haven't had any experience with the BB, but the S4's primary drain is the screen.
Having reduced screen brightness to about 25% I was able to use it for 37hrs from full charge, with numerous calls/mails and always being connected to wi-fi in the office and at home. I believe it's possible to drag it further with further tweaks e.g. using EDGE instead of 3G etc
With screen brightness at 100% the battery drains the next day in the morning. YMMV
Another thing to consider is stability - I haven't had any hanging issues with this phone, given that I consider myself a pretty heavy user (youtube, mp3s, movie streaming via DLNA in my free time). It's now 2 weeks straight without a reboot and no slow behaviour.
As a businessman/techie I'm satisfied with the S4. No complaints :)
HTH