Which one is better? Office 2019 or Office 365?

Depends on the features you need.

Office 2019 is the last "stand alone" version of the Office program.  It is designed that you purchase it once, install it on your PC and everything runs from there.  For home use, it is a good option.

Office 365 is sold as "SAS"  (software as a service).  You purchase and stall the program, but then you have to continue to pay an annual fee to keep it working.  It includes Office 2019.  But also a lot of additional programs such as "Teams".  It allows you to install the program on up to 5 computers.  It gives you storage space on the cloud for storing and backing up files.  It gives you access to an Internet version of Word, Excel, etc. that you can run from any computer even if Office is not installed.  And it allows the hosting of email/Exchange servers.  All features that most companies need and want.  365 is the better option of an office or small business account.

A third option is either OpenOffice or Libra Office.  Originally the same program, they split a couple years back because of a copyright dispute about one of the options in OpenOffice.  Both are free clones of the Microsoft Office program.  OpenOffice has been around since the 90's.  It is 100% free.  It includes version of Word, Excel, PowerPoint, Access and an email client.  It can open and edit documents created in any version of MS Office.  Any new documents you save are 100% identical to MS Office documents.  (Or you can save them in a format that only OpenOffice/Libra can read)

The interface looks a little different from MS Office.  There is a slight learning curve because you have to figure out where some of the features are because the menu layout is a little different.  But once you figure those out, it works just as good as MS Office.  And it is free.

Note that Microsoft is currently in the process of forcing people towards Office 365.  (They make more money off it then the other versions.)  The latest update to Windows server prevents you from installing early versions of Office on to servers.  It probably will not be long before they also block it in Windows 10.  If you purchase 2019 you may only get a couple years use out of it before MS kills it.

Open Office will still be here - and free - once everything but Office 365 is gone.

open source LibreOffice

I am still using office 2003 and it works fine

I wouldn't pay for either one, but if I absolutely had to get one, I would go for Office 2019 (or whatever the by-year release is). At least I wouldn't need to buy it ever again.

I do think Office 365 is better.

Libre Office is a free

The 'better' one is which one provides a feature you need that is not provided by the other. It's all relative to each user.

MS Office 2019 is the best.

neither , you use at the most 10% of the functions in office anyway , so why dont the cut the functions down and sell it cheaper , after all office 2004 would do anyway .

Office 2000, no ribbon and the menu makes total sense. Why did they ever revert back to the Wordstar-style interface?