I struggled with the same question. From my own experience, free fax tools work okay for occasional stuff, but paid services add reliability, faster delivery, and better security. After reading
https://tech4blog.com/ , I realized that for sensitive or frequent documents, paid options save a lot of headaches. I once had a free fax fail during an urgent contract submission it was stressful. Now I stick to paid services for important docs, but free tools are still handy for light, low-risk use.