The Ultra has a PCIe x1 slot, and the SLI does not. So in that sense, the Ultra does have one feature over the SLI, which is an extra PCIe slot.
The Ultra's PCIe x4 slot replaces the SLI's "extra" PCIe x16 slot. The SLI's x16 slot can do everything the Ultra's x4 slot can do and more...