poll: crib mattress - foam or springs?

We finally got LO (little one)
Put him in his room.
We picked everything except the crib mattress.
So I need your opinion.
Foam or spring? Why?
If you like or hate the mattress, let me know the model and model of your mattress.
The budget is $ 100ish, so don\'t bother to recommend your $400 all natural coconut low allergy organic crib mattress, thanks! ! !