Not really any difference but people would rather have a UK one, only sold as limited numbers and hold their money like nobody's business. Looking at upwards for £50k for one. Imported ones can be had for less and there are more of them but you pay more for insurance on an imported car in the UK and it can be harder to find insurers whilst UK cars are cheaper to insure and can be covered by a lot more companies.
I believe the only officially imported and registered R34 in the US belonged to Paul Walker. He was also a GTROC member who posted. He loved his Skyline GTRs