Choosing a crumble topping

I notice that in her crumble section Delia sometimes uses different flours: plain or self raising. Is there any particular reason for this?

I'm asking because I want to put a spoonful of her crumble on the side of a plate of cheesecake. I saw this idea in a restaurant and thought it complemented the cheesecake perfectly.

Which of Delia's crumble toppings would you recommend for a basic cheesecake

As always many thanks for been here for us.

Kevin