Calling all Northern Rhone enthusiasts, stylistically speaking, what do you think the differences and similarities between these two regions are?
What are some of your favorite producers within them?
From my experience there are far more differences within the appellations than between them. Parts of each AOP are on steep hillside vineyards and large parts are on flatter lesser quality plots. You will commonly see both in box wine format in France at very low prices, but both are also capable of outstanding wines—if they are from the right locations and in the right hands.
Benchmarks for me in St Joseph are Chave, Faury, Cuilleron and Gonon; for Croze try Guigal or Graillot.
Graillot is my favorite "value" Northern Rhone, and it actually comes from the alluvial flat lands... i think the guiraude bottling does too.
Those others are my favorites as well, even though Gonon is such a PITA to find at a decent price these days.
Alain Graillot is one of my favorites as well. I tried his recent 2015's and with some double decanting they are already drinking very nicely (St. Joseph really meaty and bold, Crozes Hermitage slightly softer and elements of black tea). I also blinded the 1996 Crozes Hermitage and it was true to the style; peppery, soft brambleberry fruits, and still holding its body.