I would avoid making a driver decision on this basis for normal domestic applications. Some have had problems with foam in the past in certain areas, however many such as Adire, claim that foam surrounds are now vastly superior to what they were in the past.
It appears that foam is better from a performance point of view, although rubber is considered more durable.
Most of us here have an attention span much shorter than the life of a driver. We want to upgrade after 5% of its life has been lived!
Foam used to be a no no, a cheap substitute for rubber. THings have changed quite a bit. Foams are now usually encased in a film making them less subject to foam rot. And they can be tailored to allow a more controlled excursion. So it can be a plus. Many a high excursion driver requires a strong restorative force. Foam can provide this without the sacrifice of weight that rubber will penalise a suspension with. ( rubber can pull this off. it's just that foam is usually cheaper and lighter. lighter means that the motor strength can be less and still produce a decently efficient driver ) SO personally I would not be to worried about a quality foam surround.
A tip to make sure that the foam is coated is to look and see if the foam has a slight sheen to it. When they are coated they last a long time. Even the moldy oldies lasted quite awhile. I had some Ratshacks that lasted 15 years before the foam rot got the better of them. And there are a bunch of 15" in the basement that are over 10 years old and still non the worse for wear!