Bean bags - foam or beans? what size?

[KrisM]

I'm trying to decide what to buy for the kids. I want them to be able to use them for years.

So, are bags with foam inside much better than those with beans? Is it worth the additional cost?

And, what diameter? The kids are 3, 5, and 7, but I do want it to be able to be used for a long time.

There are too many choices!