Hi jasonmolinari,
Outside of the physical strength of a foundation and the amount of weight it is designed to hold and the amount of flex and sagging that it allows in either the short term or long term, you can read a little more about foundations in general in the foundation post here and in particular the two posts that are linked in the second paragraph. There is more about wire grid foundations in post #10 here and outside of any strength concerns with a foundation that has fewer slats you can read more about a foundation that has a solid surface (such as cardboard or a solid surface platform) that doesn’t allow airflow as easily in post #10 here.
I believe that of the two you mentioned the Simple Life foundation would probably be the stronger and overall better choice for your mattress.
Phoenix