I'll try to list all the pros and cons. The only reason I bought a second one was to play games with my sibling that lacked local couch co-op. I got the newer version of the original model and not the Lite because I need TV mode and I don't trust the built in joy cons to hold up.
Pros:
- Can have a different purpose for each one (one travel, one for home or one for one room and one for another room).
- With multiple copies of games you can play with someone else together.
- One switch breaks, you always have a backup.
- Multiple save files for games that only allow you to have one per Switch.
- Storage purposes for if you only want certain games on a Switch to avoid clutter (better off just getting a big microSD though)
- Homebrew if you intend it for offline use only (I won't say anything more than that to respect forum rules as there are plenty of videos on Youtube if you are interested.)
Cons:
- Internet check required for digital games and downloadable content if it is not your primary Switch. Go with physical copies and you can pass the check (except for DLC).
- Requires you to buy multiple copies of games if you intend to play non-couch co-op with friends.
- Games that are not supported by cloud backup will require you to manually transfer the saves between systems which will erase your play time and is inconvenient.
Overall, it was definitely worth it to me to get a second one. I can play mine in my room whenever I want and my sibling and I are able to have our own separate Animal Crossing islands, play Splatoon 2 together, Pokemon Sword/Shield together, and others! Just think if you intend to use it for anything else aside from Animal Crossing. That will still probably net you tons of hours working on a new island which might be worth it, but I personally only think it's worth it if you plan to use it for any other games and reasons as mentioned above.