Short songs - anything upto 3mins
Long songs - anything over 6mins.
Myself, I prefer long songs. They need more attention. Some songs can drag on a bit if the band haven't done enough to make it interesting e.g. Wilco and Mars Volta in their 'White Noise' phase. Don't get me wrong, I do still like short songs - Futureheads' debut is still one of my favourite albums.
Which do you prefer?

Long and hard for me
both good
next
depends
on what the song is, no? That's like saying cold food or hot food.
Good point.
Well made.
Don't give up that easily!
Easy
I like hot food
I (generally) like longer songs.
I'd rather be left wanting more.
Too many people don't have the balls self edit enough.
^
definately.
short albums and short live sets are my favourite.
no matter how fantastic an album/live performance is, if it hits the point when you start to lose interest slightly it spoils the whole thing.
i'd say Yankee Hotel Foxtrot is a perfect length record for me, but I Am Trying To Break Your Heart is pretty lengthy (and great all the way through).
MEW
i agree about the futureheads etc. i think its good to vary it about. i dont think it should "define" a band to be good at short or long songs. i think Mew are one of the best at doing this, using amazing melodies, but not overdoing it in the sense that "chorus mongers" like the fratellis do so cheaply.
..
Any song off Double Nickel On The Dime vs Marquee Moon. Now I am confused.
I like good short songs and good long songs equally
I prefer bad short songs to bad long songs as they finish quicker.
I think I just like good songs
I think I like songs the most
(those between 3 and 6 minutes).
However, many of my favourite songs are long songs. Although in general: songs > long songs.
i think those are medium songs
also good
The funny thing is
The types of music I like specialise in extreme short songs and extreme long songs.
My love of Minutemen, Descendents, Minor Threat, early Husker Du etc points me towards short songs, but nothing beats a towering rock song with a huge fuzzy riff.
So I don't like Medium songs. Extremely short, or extremely long, please.
p.s
Guided by Voices, Minutemen and Sebadoh do shorties best.
and
Yo La Tengo do long'uns best.