Usenet and e-mail are closely related; there is a reason for Usenet to exist.

There exist gateways between usenet and mailing lists, too.

If you join a new mailing list, your only option for "back issue" content is to go through an archive. Either a web archive, or else mbox files.

Usenet has a pull model. You connect your client to a server that stores articles going back whatever: months, years. You're not subscribed to receive anything spontaneously; if you want to quit Usenet, just exit the program, and that's it.

Numerous newsgroups are available in one place; you can search through them in your client and take a look. Mailing list archives tend to be scattered all over the place. GNU mailing lists here, BSD mailing lists there ...

On Usenet, you never have to use an identity with a real, working e-mail. Not so with mailing lists; they don't work without a reachable e-mail address.

Usenet has spam and so do mailing lists. But mailing lists have actual e-mail spam. Not only are lists sometimes the targets of spam, but spammers harvest addresses.

So, when I subscribe to mailing lists, I use throw-away addresses, unique for each list. This is a dance I do not have to do with Usenet.

When you use different addresses for subscribing to different mailing lists, you have to be careful to also use the matching addresses as your posting identity! (If you use your principal e-mail address by accident, it could get harvested. Or, something else: the posting might not go through to the list at all, due to that address not being a member.)

When a throw-away mailing list identity receives spam and you replace it with a new one, your old identity still exists in ongoing discussions and will be CC:'d in new postings.

You can use a working e-mail address in your Usenet From: header, if you choose to do so, so that you can be privately contacted. Getting a private e-mail reply from a Usenet posting is rare. If that address starts getting spam, it's pretty easy to change, just in your NNTP client setup. The address is not the basis of your NNTP identity, and so changing it doesn't break threads.

It doesn't involve your mailbox in any way. You don't have to register. "Subscribing" to a newsgroup is purely a local configuration, and you don't have to do that to post to it.

When you sum it all up, Usenet is easier to use and more casual than mailing lists. That gives it a different flavor.