In reality, they are the same language so to debate whether is discussion is meaningless.
You can read and understand both. I don't see why some sites or people have a favorite between English (U.S.) and English (U.K.)
It is the same thing.
It is... but at the same time it isn't. Words can have different meanings, can be said different, and have different spellings. It is honestly hard to understand what somebody is saying if they were to use a word with a different meaning than what is known to another person. That is unless the person has heard that term used beforehand, and knows to expect a different meaning. For example, in the U.K. when someone says Knock-up, it is most commonly meant to say "to wake somebody up", but in the U.S., the term is usually intended to mean "To make pregnant". Both have completely different meanings, but are said in the same way.
Or if you are asked to knock some guy up? what would it mean then?
Yeah, I was having a fag when I knocked him up!
OMG was it bloody? is your boyfriend OK?