Is USB3 important? Only if you buy USB3 peripherals that need the extra speed, like external hard drives and such. It won't make any difference if you only connect stuff like a keyboard and mouse. Besides, you can always add a USB3 card in later.
USB 3.0 has significant faster data transfer rates over USB 2.0. It is also backward compatible with USB 2.0 devices. For a new rig, it is nice to have all options intact. This I will recommend you to go for a motherboard which has all the latest features. You can find that Intel board for lesser here -