Is DAW or Dorico easier for orchestration?

That really depends on your workflow, and on the end product. If you are looking to produce something that will be played by live players, you’ll always end up using Dorico (or Finale, or Sibelius, or other engraving applications). Many DAWs have built in notation but I really wouldn’t use that to create scores and parts. If you are looking to create something that sounds as good as possible without having live players, then you will find that a DAW is more flexible and has endless options to tweak how instruments sound, use audio files, automation, and so on.

In the film music world it is customary that scores are first written in a DAW. The composer tries to make a midi mockup which sounds as good as possible (sometimes they employ people who do this exclusively, they are called “programmers” in Hollywood). Once the mockup is approved by the director, depending on the music budget, the midi files are then given to orchestrators who prepare scores and parts for live performance. Sometimes composers do their own orchestration, but more often than than this is outsources, for two reasons: 1. many film composers simply do not have the classical music training and background to create proper scores and parts; and 2. even if they do, the time pressure is so great that it’s just not feasible to create scores and parts in time for the recording session.