I believe that America has the best variety overall, from MM to high grades to factory pipes, America has something for smokers on all levels. America's "second chapter" in pipe making is really setting the bar high. Right now the high end makers really pride themselves on quality which I believe is a key factor in current times. They have led the way with sandblasting as an art and not just a finish to hide flaws, are developing a unique American style, and have opened a pipe factor (briarworks). On top of that, the high end makers share and discuss with other makers, quite openly and for free, ways to improve. I think if they added a couple more vowels to their last names they call all be going for a couple Gs a pipe.
Briarworks is a young factory employed by artisan pipe makers, and I think they will be sought after pipes decades from now. This feels important to mention. I took a tour of their factory, and they are more focused on quality over quantity. It almost resembles the W.O. Larsen crew or Stanwell crew from the 70s. Years from now when their estate market matures, people will be happy to say their Briarworks pipe was made by Pete, Todd, Sam, Bill, or Micah. I think that is pretty cool.
I dont have to say too much about MM. The entire pipe smoking world is pretty familiar with them and their quality. I will say that I have smoked corn cobs being sold here in China, and there is no reasonable way to compare them with MM. I still smoke the MM cobs I bought many years ago, the chinese cobs were either thrown away new or mid-bowl.
Just my 2 cents.