Well Windows 7 is best in terms of security but most popular nowadays is Windows 10 and is mostly used by people.
Windows 10 is mostly used? Stop spreading misinformation as this is false. Windows 7 is by far the most used operating system, accounting for
over 50% of all installed operating systems. Just because Windows 10 is being offered for "free*" that does not mean that anyone should upgrade to it.
Why do I feel like this conversation is comparable to talking about religion?
Pretty much more conversations in this part of the forum are. People are basing things on their personal, ergo subjective thoughts. Just because someone is using e.g. Mac that does not mean Mac > Windows.
*free - Your data being mined and sold.