LeGuin's "ansible"
The lifeblood of civilization is information. The faster information can travel, the farther a civilization can spread, yet still be connected enough for distant members to recognize their common citizenship.
On the multi-star-system level (or larger: galactic arm or entire galaxies), a technology that had physical FTL travel but had to rely on the EM spectrum to communicate would be, IMO, at a disadvantage to a tech that could communicate instantaneously, even if they could spread colonies no faster than Einstein allows.
As far as I know, LeGuin was the first to introduce the device.