That is a good question and the answer is relative, you asked which one is more secure for messaging and you did not mentioned privacy of anonymity features which are tied to the concept of secure but not a must.

You missed probably, in my opinion one of the top 3, which is Session...

All three offer you a great level of security in the areas of privacy and decentralization but out of the box only one anonymize you, which is Session...

nostr:nprofile1qqsvnx99ww0sfall7gpv2jtz4ftc9v6wevgdd7g4hh7awkpfvwlezugppemhxue69uhkummn9ekx7mp0jwtjpy is the best choice for most people because its UI is simple enough, no email or phone number required, although ***if you are not using your own Server you are subject to data logging from a third party...***

Session Messenger on the other hand is all onionized, no need for your own server/node/relay, you are cover in all fronts out of the box for voice, messages and videos.

Nostr is excellent, but not out of the box, you need a client with NIP - 17, one that let you choose proper relays (your own preferable) and full privacy using TOR built in. Hands down Amethyst for Android does the job perfectly, but you need to do some configuration yourself,select privacy to full in settings, select proper relays, install your own relay even better and let but not least, sign in with Amber with TOR enabled. So not for grandma and grandpa, errrr, not for most people at all, hence why Primal gets so many users despite failing in privacy and security (is getting better) but easy to use from the get go. nostr:nprofile1qqs84k6jpsav0jmdeqjn2zxlpnsajaw6f8l0m2d4e9t8gjsyn53s4nspzamhxue69uhhyetvv9ujuumfv9khxarj9e3k7mgpz3mhxue69uhhyetvv9ujuerpd46hxtnfduq3vamnwvaz7tmjv4kxz7fwdehhxarj9e3xzmnyhat8ky 0xChat is worth mentioning, pure art, I will say a must have for E2EE messaging and calls, but the onion routing requires proxy configuration, from the test I have performed, better Orbot... That may change soon, they may add TOR as Amethyst has, time will say, that could bring more adoption into Nostr but I wish a 0xChat Messenger more like SimpleX, the UI is still hard to understand for Grandma, and if grandma doesn't get it, you are not doing it right... you want adoption, you need simplicity out of the box.

So, if you know what you are doing and the people you want to chat with and connect are into Nostr and understand the tech, go for Amethyst full privacy or 0xChat with Orbot.

If you have non Nostr people you want to keep in touch, perhaps is best to introduced them to Session or SimpleX Chat using your own server

Hope this helps