Long v's Short?

Now that winter has arrived I have a big dilemma!...

Do I go for the long running trousers or the 3/4 ones? 

It might be too soon for the long one's as it's not actually that cold yet but I was very chilly on my run last night. I don't want to peak too early and I have no other layers to call in when it gets really cold. 

Any thoughts from readers on this would be appreciated! 

So Long or Short?