hard to say from inside the company, since you get to thinking of everyone as just colleagues who happen to be working on different parts of the system. but in terms of larger world prestige I would say the machine learning folks are definitely up there, also the internet/petabyte scale stuff that other developers know enough about the difficulties behind to be impressed by (spanner for instance), and perhaps go since it has achieved a massive amount of popularity. I honestly don't know if there are currently any end user google products "sexy" enough that working on them is extra prestigious.
You're missing webranking, and other core components of core products. Deciding in which order results pop up on google.com is both very challenging and we'll recognized. Same with people that do ad ranking, people that manage the enormous storage systems, etc. If it is core to the company it is prestigious, you never have to explain the impact of your job.
