>>11588457In terms of total density, maybe, but not Isp.
Regardless, actual per-launch performance (assuming each launch gets you meaningful payload to orbit) becomes less important than ease of reusability once you have a reusable rocket. If switching from one propellant to another increased payload by 10% but also increased launch costs by 10% or more, then you're effectively moving backwards. The best strategy is to target cost, not performance.
Take Falcon Heavy vs Delta IV Heavy. Delta IV has the better engines by a long shot. Delta IV Heavy gets more payload to orbit per kg of propellant than FH. However, Falcon Heavy gets more than twice as much payload to LEO, and more payload to ANY orbit, than Delta IV Heavy. FH also costs about a third as much as Delta IV Heavy.
Why? It's because despite having much less mass, Delta IV Heavy is a significantly bigger vehicle, using a propellant that is much more difficult to handle and use in an engine, and due to that propellant's low density needs to shave every fraction of a gram off of its structure in order to make any gains whatsoever over less efficient but more dense options.
The only time you target performance is if you NEED performance to accomplish the mission the vehicle is designed for, which in Starship's case is Mars missions. If SpaceX were not looking to send things to Mars they'd probably have just developed a new Merlin engine that used a torch igniter and methalox propellant, and clustered a shitload of them onto both parts of a large two stage to orbit vehicle.
