Ah really, didnt realise that, I remember Maine Road use to be massive
Maine road used to be the biggest with Old Trafford just behind it. WHL was one of the smallest, but I think all pitches have to be 105m long by 68m wide I think.
At least it stops teams like Stoke cheating and narrowing or widening their pitch depending on who they were playing.
Old pitch sizes can be found here http://soccerlens.com/premier-league-pitch-sizes/3683/