by Hannibal Rex
Obviously, if you have both you can be a lot more flexible in your ship builds, and the initiative bonus will also play a role. And if you're going for missiles, the Positron Computer is plainly better.But otherwise, you also need a better power source if you want to use two Positron Computers, or combine one with anything better than an Ion Cannon. Whereas a dreadnought with 4 SHs is a very formidable ship, requiring only a single ship part research.
Likewise, Sentient Hull is the unquestionably best upgrade to fight (basic) ancients with interceptors.