I've never done side by side comparisons of the two with same yeasts and grain bills so I can't speak from good experience. But, here is the data from Hopunion. The chemical analysis shows some differences, like you'd expect from any crop grown on different parts of the planet. FWIW:
UK:
Alpha Acids 4 5.5% w/w
Beta Acids 2 3.5% w/w
Co-Humulone 20 25% of alpha acids
Storageability 65 80% alpha acids remaining after 6 months storage at 20o C
Total Oil 0.6 1.0 mls/100 grams
Myrcene 20 26% of whole oil
Humulene 42 48% of whole oil
Caryophyllene 12 16% of whole oil
Farnesene <1% of whole oil
US:
Alpha Acids 4.0 5.0% w/w
Beta Acids 2.0 3.0% w/w
Co-Humulone 20 25% of alpha acids
Storageability 65 80% of alpha acids remaining after 6 months at 20oC
Total Oil 0.5 1.0 mls/100 grams
Myrcene 20 35% of whole oil
Humulene 35 45% of whole oil
Caryophyllene 10 15% of whole oil
Farnesene <1% of whole oil