>>714267563annoying answer but it depends on your preferences
world is definitely the more popular of the 2 and has a more active playerbase. Obviously a lot of people have moved to Wilds but World still has a committed playerbase - you will be able to findpeople to play with if you don't have friends either online or via its 'matchmaking' system. it also plays a fair bit slower than rise (and wilds) - the areas are bigger, there's a lot more 'hunting' e.g. searching for tracks and evidence of monsters before fighting them.
Rise doesn't have much of a playerbase at all anymore, especially before endgame, so if you want to play it multiplayer you'll either need friends/discord or you'll have to progress through the main game. But the gameplay is faster and arguably more fun - you're getting into fights with monsters much quicker, the movement is expanded and quicker, etc.
They're both great games.