Answer: One is more modern -- see more below
Step-by-step explanation:
Super Mario Party was released back in 2018, while Mario Party Superstars was developed more recently in 2021.
We imagine that these board-esque party games will objectively have better ai, built-in probability, and arguably better graphics, though one may argue that the more nostalgic a game is, the better.
If your question ultimately revolves around which one you should purchase, there are plenty of factors to consider, cost, playtime, difficulty, art-style, etc. Consider watching clips of the game on your preferred streaming and video platform and reading up on their respective wikis to determine or at least further influence your choice.