I think this is a view that needs to be approached carefully. The older cultivars growing now may represent just a few of what was new when they came on the market. Those that got relatively wide distribution AND proved to be strong growers, either widely or in specific regions, can be seen as sturdy growers. Those probably shouldn't be compared to all the newer introductions until time has done the job of separating the sturdy growers among the new things. Older varieties that weren't sturdy growers have probably just fallen by the wayside and are forgotten. I don't think many people have ever grown all, or even a high percentage, of what gets introduced to the general market in any given year. So both long term vigor and how widely they were distributed comes into play, but it's really difficult to compare them over a span of time and make a conclusion. After the new ones are out for a few years, it will be the vigorous growers that had wide distribution that are left. The weak growers and those that didn't move probably won't be extant or common anymore.
