Understanding there are differences from one line/strain of a variety to another...one is closer to the "standard" in a given area than another...there are general, almost overall, differences between varieties other than just colors & patterns.
It may have been years since I personally have bred some varieties, but there have been few Ameraucana National Meets that I've missed over the past few decades. By looking at the birds exhibited by many fanciers those differences can be seen and studied.
I've mentioned many of the problems different varieties are prone to several times and searches on this forum will reveal some. In general bantam silvers don't have nice pea combs, bantam buffs are too broody for me, large fowl wheatens/blue wheatens and silver lack the good Ameraucana type we see on the others, large fowl brown reds are too small and large fowl buffs have already been mentioned.
The LF blues being shown are better in recent years, by having the required lacing, but I imagine many are still lacking in that area in backyards were fanciers are still crossing blacks with blues. It takes concentrated breeding programs/projects to make improvements like that, but it doesn't take long for it to be lost.
Even though I've said LF black is the variety closest to the standard, I still have problems with good eye color and full muffs in my line. With just those two faults at the top of my list it shows how far they've come in 30+ years, but I also know that there are other areas that can always be improved upon and the perfect Ameraucana has yet to be found.