Foam or Innerspring (Marshall Unit) Cushions

My wife and I are buying a Bernhardt sofa at a local furniture store in Austin, TX. We can choose between foam core cushions and innerspring core cushions at the same price. We tried both in the store, and hey both feel about the same comfort level and provide similar support. I guess it really comes down to which one will last longer. Do you have any advice? I am about 300 pounds, so durability is a key.

I realize Bernhardt is not the "best", but for our price range, we feel like it is a good choice for us. The sofa with the sale deals factored in comes out to about $1400 before tax. Thanks.