Flutter seems to have a lot more people using it atm @pillaiindu - and this usually equates to more books, videos, resources etc. For instance there’s @carminezacc’s #book-programming-flutter but I don’t know of any NativeScript books.

However as mentioned in response to @DevotionGeo’s post I would delve a little deeper into both and see which one you prefer yourself… but if I were choosing right now I would be leaning more towards Flutter because I really like learning from books

There was a blog post titled How NativeScript works which isn’t there now, but you can find it at this link at web.archive[dot]org.
To know how flutter works, read Flutter architectural overview.

It’s not an answer to your question, but I think knowing how something works is more important than how “easy” something is.

The book @AstonJ mentioned, Programming Flutter, contains an Introduction to Dart (Appendix 1), which is enough to get started with the book.

Edit:
For NativeScript, I suggest starting with NativeScripting free courses.