GB&I wins in my book.
After the top US 50-60, the courses get more and more landscaped to the point where the need to play them again rapidly diminishes. Meanwhile, the GB&I courses remain rooted in nature, plus they possess more variety from nine holers to one-off courses like Shiskine. Finally, the GB&I courses are a lot less likely to be over-maintained.
Perhaps the top 100 just from England would be more interesting to compare to the US? Wonder what Paul Turner might say to that?! I imagine that the US's top 20 (NGLA, Pine Valley, CPC, Pebble, Sand Hills, Merion, Shinnecock, Fishers, Seminole, PacDunes, Friar's Head, No.2, Prairie Dunes, Riviera, Garden City GC, Maidstone, Crystal Downs, Oakmont, Winged Foot, and probably still Augusta) is strong enough to carry the day vs. just England.
Cheers,