Despite the words 'blow' and 'suck' meaning exactly the opposite, there is no difference between the two expressions. In terms of usage, 'It sucks' is very common in the UK, but I've never heard anyone say 'It blows' here, although everyone would understand it. EDIT: Good points Paul: they are both definitely American, I mean to say that 'it sucks' has leaked through into colloquial use here (if only in certain groups) much more than 'it blows'. Hopefully tone and context combined with American television programs would bridge the gap in understanding them.

In colloquial usage, to mean that something is bad, boring, stupid, not fun, etc., there is no difference. In regular usage, it depends on what "it" is. The wind blows and vacuum cleaners suck If "it" is a performer of fellatio, there is no difference.

As far as I understand, there is only a difference with regards to the context and subject and whether the phrase is being used for an indirect or direct object, which has been mentioned before. If something is bad, boring, stupid or no longer fun then "it blows" or "it sucks". Change the object/subject you are referring to and the meaning changes. If you're talking about how good the vacuum works, "it sucks" up the dirt really well. If you're talking about the wind - it blows or it blew the clothes off the washing line. You do not necessarily need to have the object or the situation at hand however to use that phrase. You could be talking about a class you attended earlier and say - it sucks. There could be a situation between you and a friend and - it sucks. Or you could be talking during dinner, to friends/family, about how hard you worked on your studies only to get a grade that wasn't as good and - it blows.

I consider "it blows" to be a more intense way of saying "it sucks." We tend to use "it/that sucks" so often that the phrase has lost a lot of its strength. So to make up for the loss of meaning and to point out that a situation REALLY does suck, I will use "that blows."

Hello. In terms of colloquial usage: I am based in the UK and now in my 20s and I have not ever heard anyone say 'It blows' to express that something is bad. 'It sucks' was/is common among young people. Also common as an expression of sympathetic acknowledgement, eg when someone tells you something bad has happened to them, 'That sucks' 'That really sucks'. However, have absolutely 0 statistical evidence for these claims, but I've used and heard used the phrase 'that sucks' a lot but never used or heard the phrase 'that blows'. But they do mean the same thing.