If it is working and you manage to get around the problems during updates.
For 10€/month you get a vserver with much more RAM. I would chose this way if you wanted to expand the usage of Nextcloud. Get familiar with server, install and maintain them just for 4 calendars and contacts… that’s not worth it. And before doing that, try it at home with a virtual Server (VirtualBox) or a Raspberry Pi on your local network. And then find a hoster that hosts you directly Nextcloud.
Likely not necessary given your usage - 4 clients, just calendar and business cards. You likely won’t see any benefit with extra memory. Save your money.
That said you should not get errors when updating, so that suggests a bigger problem. How did you set this up - as an e.g. docker container on a hosted VM? If so, maybe your host can advise on your errors (could be your system of theirs). Else posting the errors you see when you update on this site might get you some pointers to a solution that fixes the updates (and still allows you to keep your euros).
I today decided to change to a new hoster who offers 512 MB Memory and on SSD storage for almost the same money.
Then I installed Nextcloud (ftp upload). In order to test if the internal updater works, I then updated to the latest beta. It ran without any problems.
I think NC benefits from a 512 MB Memory Limit. Maybe not during the normal usage, but when running an update.
If an update by the means of SSH is available, it might be no problem, but the web updater is tricky.