Great variety of cultivars. I tend to rely on (a few) New England asters which have deep colours and seem to live longer than New York asters here.

My limited experience of New York asters agrees with what one reads; namely, that they are often more branched and more compact than New England asters. Also, that the flowers are distributed more evenly over the whole plant (rather than located at the top of stems, as with New England asters). I do find that they bloom a long time
here.

A lot of them are evidently hybrids.

I'm so-so on the pink New York asters, but do like the powder and lavender blues (e.g. Henry III).
See below (October 15, 2013).

The hybrid asters commonly found in garden centres are usually the dwarf cultivars such as Wood's Light Blue, Wood's Pink, Sapphire, Prof. Kippenburg, etc. They can get leaf diseases during rainy summers, but are otherwise reliable fall bloomers, if the rabbits don't eat them first. Most of them are hybrids of several species asters, including the New York aster.

Thank you. I'll give them a try!