I consider The Exorcist the greatest horror film ever made. As for which is the best version, I think the original cut is the most alarming, as it excises some bits and pieces in the ending that emphasise good has triumphed, despite the cost in human life. However, overall, I prefer the extended version - not so much for the spider-walk, but for the priests' conversation on the stairs near the end, mid-exorcism.

I have a complicated relationship with this film that you can read about here, if you're interested (I expect you will be, given your Christian upbringing). :)

https://simondillon.medium.com/are-we-allowed-cancel-cultures-illusion-of-authority-d68ab8312711