Scrivener 3 brought the word count more in line with Word as it now counts hyphenated words as only a single word (previously a hyphenated word would count as two words or more, depending on the number of hyphens).
One thing to bear in mind is that when you Compile, titles and other elements may be added which will increase the word count. You can find the word count for the text as it would be if you compiled it using the current Compile settings in Project > Statistics…
Other than that, there will always inevitably be slight discrepancies between word counts in different apps, depending on the algorithms used. Scrivener uses Apple’s word recognition algorithms (with the refinement added for hyphenated words). Word’s algorithm may be different, but it’s not “better”. In fact, I just pasted several chunks of text into Word and it came out with a larger word count than Scrivener each time. And a couple of hand-counts showed Word to be wrong (I’m not even sure where it was getting the extra words from). I understand that Word is the standard, though, so that this isn’t particularly helpful, but all apps will have some disagreement with word counts. Apple’s is pretty good, though.
All the best,
Keith