Launch first, then use their launch as free publicity : on each news on their launch, comment : "hoo nice, but that's just like Xxx" (well, add more value, do not spam heartlessly)
The worry isn't so much the PR. It's an all-round "were going to get our arses kicked", due to their combination of talent, funding, execution etc, unless we find a unique angle over them. Their execution is ... impressive. Also might be a blunt point for raising further funding unless we are different enough.
Then launch NOW and iterate, iterate, iterate fast. You think that you can't match them ? And that there can't be competition ? Competition is good, it will keep you focused.