The video was taken by PhoneArena at MWC in Barcelona, Spain. Notably, Samsung has improved its sensor and it no longer requires swiping your finger over it. You can now press and hold similar to Touch ID on the iPhone.
We'd say that Sammy's finger scan is just as reliable as the one on Apple's flagship, as each unlock attempt was met with success. Now, as far as speed goes, the Galaxy S6 unlocks just a bit slower than the iPhone 6. We wouldn't say that the difference is dramatic, and it may be more to do with software and animations, than the hardware sensor being slow. In any case, we'd say that for normal usage, not comparison and nitpicking, the sensor is speedy enough so that the user wouldn't notice a difference.
Take a look at the video below and let us know what you think in the comments. You may also want to check out this speed comparison video.