What rear hub spacing?

the rear comes in a 120mm or 130mm spacing. Which should i get? from what i can figure most track frames are 120mm?? I dont want to pick the wrong one then limit myself to frame choice when i get round to it.

You've already been told by the chaps above but, speaking from very personal experience, go 120mm... You'll save yourself a ton of cash (trust me) and be able to swap stuff in/out as and when you want to...