Car seat

So I currently have the chicco keyfit for my LO and love it! He’s starting to get too big for it so I’ve been researching other car seats. Before researching I was just going to go with the Chicco Nextfit because I love his infant seat so much and it is the highest in safety ratings. After researching it seems that the nextfit isn’t that high on safety ratings and that basically across the board the Britax Marathon convertible seat is. I know the nextfit didn’t come out too long ago and was wondering if maybe it isn’t as high on its ratings because it hasn’t been around as long so the consumer ratings aren’t as high? What do you guys think and out of these two which would you choose or do you have??