the 1 is UHS 10MB/sec, and the 3 is UHS 30MB/sec. Note that's megabytes, not megabits.
From what I can tell, C10 and U1 are basically the same speed, but I think there's a new communication technology at play there; the page here shows them being used interchangeably on cameras requiring U1 or C10 cards, although it looks like you can't use a C10 card in a camera that is only rated for UHS cards.
Here it is: "UHS (Ultra High Speed), the fastest performance category available today, defines bus-interface speeds up to 312 Megabytes per second for greater device performance. It is available on SDXC and SDHC memory cards and devices."