Definitely the UK, simple and often based on historical precedent and identifiable areas. For example, Woverhampton North East. Its simple and accurate, the seven most northeastern wards in Wolverhampton City Council.
If the UK did use the US numbers system, how would we know which of 600-660 seats was where ?Would we have to put them into smaller categories? Would Ludlow, for example, be seat 300, West Midlands 18, or Shropshire 5?
The Rt. Hon. David Cameron, Member of Parliament for Oxfordshire's 1st Parliamentary Constituency doesn't exactly have the same ring to it, you're right.