In my opinion:
Meshtastic is MUCH easier to set up. Reticulum is very difficult to set up and requires a lot of time/work at the moment.
Reticulum has a lot of potential for more protocols, networking, apps, etc…
Meshtatic is very much made for messages and finding nodes.
Both work with LoRa.
Ive played around with both and was more successful with meshtastic (and meshcore). But Reticulum impressed me because I could send images over LoRa and could work with just about any networking. Which was interesting!
This is a good video showcasing RNode/Reticulum here: https://youtu.be/BsAMeMp1hlg?t=657
Theres MUCH more to it, but in nutshell it allows you to do TCP/IP/Internet things with LoRa. More info here: https://reticulum.network/
Its a network of networks.
I was able to communicate with another node via voice and images through LoRa. Its very useful if you are looking for more of a internet kind of mesaging system but VERY hard to set up (my opinion). Looks like the community made the heltecs work on it now which was fun to play around with.
You can see an example of this in the times link above.
Sounds like Reticulum is what you need for an actual decentralized internet, while Meshtastic is just a messenger service.
I think thats what they were going for. And it seems to function that way.