In article .com.au,
Daniel Hanna wrote:

In m Shiva wrote:
Just an observation, no theories or claims etc. But I am thinking I'm
not going to buy anything but ownroots next year. What do you all
think about this? Can anyone offer any theories as to why this is?

It stumps me too, Shiva. Possibly the grafts are grumbling about
rootstock that is waterlogged, whereas on their own weaker roots the
plant can pace itself better in poor conditions.

Waterlogged, soil chemistry, susceptibility to nematodes, who knows.
But I've only rarely found own roots to have weak roots. But I only
have a few really modern roses.

I doubt the fact that some of them are Austins makes too much difference.
Bear in mind they are bred primarily for England's wet climate. In
Sydney Australia I find they tend to die MORE easily than HTs and
floribundas, but all mine are grafted anyway.