Watch this video if you can. From Tim Dodd of Everyday Astronaut. A bit old but still useful. Only 49 minutes long.
SLS VS Starship: Why does SLS still exist?!
https://www.youtube.com/watch?v=KA69Oh3_obY&t=231s
Right now, the SLS shouldn't even exist. It exists mainly because of politics.
SpaceX
“ The fully reusable rocket could have a per flight cost of $2-5 million for its 150 ton capacity.”
https://www.nextbigfuture.com/2020/11/spacex-superheavy-starship-size-payload-and-cost-details.html
SLS
“ The initial 322-foot SLS “block 1” version can lift 95 tons of payload and propellant to low-Earth orbit and can send 27 tons on to the moon. It is the only rocket in the world that can boost that much material to the moon in a single flight and it is the only heavy lifter that is already “human rated.”
Future block 1B and 2 variants, the former using a more powerful four-engine Exploration Upper Stage and the latter using both the EUS and more powerful boosters, will stand more than 350 feet tall and be capable of lifting between 38 and 47 tons of payload to the moon.”
https://www.cbsnews.com/news/nasa-moon-rocket-artemis-mission/#app
But to SpaceX, again
“ SpaceX says the 394-foot-tall 30-foot-wide rocket will be able to deliver 100 tons or more to the moon, twice the capability of even the SLS Block 2. But the Super Heavy-Starship can’t do it in a single flight. Multiple launches of Starship tankers will be required to refuel moon-bound ships before they leave Earth orbit and a major delay or launch mishap could have significant consequences.”
So today we have Artemis, and SpaceX will soon make the business case of replacing Artemis. Getting certified for manned flight is no small feat. I work in the industry. Whoever wins, America wins.
Artemis will get us moving; and if/when SpaceX takes over, good on them