When taking photos or shooting video, the image data is offloaded to a high speed internal cache for processing. There is a limited amount of space available in this cache and so to empty it out, files are written off to the memory card to make room for more pictures or frames of video.
If you take photos or video at a rate that exceeds the memory card's ability to save, eventually the cache will fill up and it will not be possible to store any more images. Using a faster memory card allows for the cache to be cleared faster and thus, you can shoot for longer before the cache fills (assuming the camera supports writing to and from the cache simultaneously) and also makes it so that when the cache does fill, it can be empties more quickly.
The one caveat to this is that if a particular type of card is not supported by the camera or the speed of the card exceeds the speed of the card slot, then there would be no gain by moving to a faster card and it could actually result in the card not working potentially.
So, to determine if the UHS1 card would be an upgrade, you need to verify that your camera supports UHS1 cards and that it can make use of the speed. If it can (or if it supports a speed faster than your current, but slower than UHS1) then the upgrade will allow for your cache to be cleared quickly and increase the available video recording time (if it was previously cache limited), increase the number of photos that can be shot in a burst (if the camera supports writing to the SD card while the cache is being written too) and faster clearing of the cache when not shooting (gets ready to shoot a burst again faster).