Your camera supports UHS (I think... I didn't look it up), but probably does not really take advantage of its increased speed. Your camera's video bit stream is the same as mine: 5.5MB/s. It has 1080p/30fps and 720p/60fps modes, but they both produce a bit stream of 5.5MB/s.
People on this board buy faster cards than strictly needed for various reasons, including bad experience with cards that don't perform as marked, the belief that their camera will take advantage of the increased speed (some higher end cameras do, but mine doesn't and I doubt yours does, either), wanting to "be sure" to not have problems, faster buffer dumps with burst shooting, and wanting faster transfer speeds from the card to their computer.
Burst shooting of still photos, even with your T4i, produces a much higher bit rate than HD video. That's why your camera has a very high speed RAM to buffer the burst shots before they are written to the flash memory card.