SOC Tools: Is Xlinx light-years ahead of Altera?

The impression I get is "Yes", but this is mostly just the way the market has gone.

Xilinx have run away with the SoC market. Altera were very very late to the party on arm, and Xilinx have had hard CPU cores on their fabric for a long time, far longer than Altera (Power PCs before ARM). I dont think Altera really have any interest in it any more, especially as they've been bought by Intel. Altera are more focuessed on getting Intel chips with FPGAs built into the fabric, rather than FPGAs with hard CPUs.