I have had a few English razors, and I don't know what it is but they seem to perform better than their American counterparts.
My favorite razor is a #15. I don't necessarily think it shaves better than a U.S. '34 Crat, but I prefer Rhodium to gold for both practical and aesthetic reasons, and the prices between those two models are not that much different. Some British models cost more because they are comparatively rarer, so if you want one you've got to duke it out with everyone else who does. I don't think the British Knacks and Techs command particularly higher prices than their yankee counterparts. I also think the chances of getting a good price on a British razor are better in England where you know they probably have more of them.
I like the looks of the English razors better than the American Gillettes, especially the Rockets. I've read that the English Gillettes are better made. I have some of the rockets at a decent price from an etsy seller, but usually the prices on ebay are too high for me and there aren't a lot to choose from. People must be hanging on to them or they are mostly in England. What about the Canadian versions of Gillette? Some look a bit like their English counterparts.
The feel of the mechanics of the British razors seems to be better. My Rhodium Aristocrat feels smoother and less rattly than any of my American made Aristocrats and a Rocket compared to a '40s era SuperSpeed feels likewise better assembled. Opinion based on a relatively small sampling of course.
I have a three piece 60's Gillette that I bought for $20 with $3 off with a coupon. I like my dad's Slim better.
Canadian Rockets, were sourced from England. I know, I have one of each (Canadian and English). It was a split scheme for Canada. Generally if the name matched a English Gillette the Canadian version would be sourced from England. If it had the U.S. name the Canadian version would be sourced from the U.S. My rockets are much better than the equivalent Super Speed for heft, aggressiveness and build quality.
Thanks for the info, Gary. I have a few Canadian sets of Old and New Gillettes and they look very like the American version. I wish I had some of the English/Canadian razors.