They take very different approaches even if they have similar goals.
Neither is better I think unless you want to get fanboy tribal. It is to be seen what apps will scale and gain adoption for each, though bluesky having a few mil in funding and normal users definitely puts it in the lead.
Speaking as someone funded in the crypto industry... nostr, IMHO, is dominated by BTC maxis and creating a monoculture around it, which will prevent adoption, b/c a social network isn't going to just be talk about NgU and HODL'ing all day.