Both, although it's possible it's only "Raiser" in some locales[1] as a typo — Uber's liability insurance paperwork[2] and site[3] refer exclusively to "Rasier".

[1]: http://tsa1.nv.gov/ActiveCertificatesDetail.asp?cCertNum=TNC...

[2]: https://ubernewsroomapi.10upcdn.com/wp-content/uploads/2019/...

[3]: https://www.uber.com/global/en/cities/washington-dc/

There's at least one document[4] where Rasier LLC forms a subsidieary `Raiser-CA, LLC`.

[4]: https://www.vice.com/en_us/article/9kwjz5/unicorn-trank-and-... , specifically https://video-images.vice.com/_uncategorized/1500911986571-S...