Unless rocket is still limited to the sync world, in which case actix-web would be the obvious choice, I'd say it's a matter of preference nowadays between Rocket and actix-web.
What got me interested in Rocket was the nice declarative way I could attach routes to handlers using attribute macros (the alternative being the old actix api which would require me to specify the routes in the main fn, which never made much sense to me). But actix-web has had the nice declarative API for handlers for a while now too.
I'm not entirely sure how rocket handles data plucked from an HTTP request, but I do like the way actix does it by making it effectively declarative. That is, if you have a route with a parameter in it, you just attach a parameter to your handler of the correct type, and boom you have access.
I'd imagine that rocket allows something similar.
Other than that, actix has historically been near or at the top of various benchmarks, but it's a bit of an open question to what degree that translates to superior real-world performance, not least because it depends on what exactly any given server is doing.