Mainly preference. I've never run the long wheelbase...just the 210 mm (Cooper) and the 225mm (Swift). I can tell you in theory the 210mm should be good for small to medium tracks having better tight track manners. The 225mm should be a good all around car and the 239mm should be a good large flowing track car. Now with that said, it's pretty much just preference. I tend to like the way the Cooper 210mm handles. For me it seems a little more nimble than the Swift.