We are the stronger species, we win. Empathy is evolutionarily expensive.
I'd say that empathy is so evolutionarily valuable that it's the fundamental reason we are the stronger species.
It seems very likely that we evolved the capacity for empathy because people who have it are more effective at understanding the points of view of others, which is a pre-requisite to the more effective forms of cooperation. It's clearly our ability to cooperate which makes us the dominant species on the planet because as individuals we're pretty weak and ineffectual compared to other megafauna.
Of course, it's only really empathy for others who are likely to be willing to cooperate with us that is evolutionarily useful. This extends beyond our own species, though, and encompasses animals whose companionship or service we value (think dogs, horses). You'll get better service from a horse that you treat well, and you're more likely to treat it well if you can empathize with it. But our brains don't distinguish degrees of utility that finely, so many animals get empathy from us, largely in correlation to how easy it is for us to identify with them. Dolphins, with their obvious intelligence, sociability and playfulness, generate strong empathic responses in people, even though as marine animals they're quite different from us.