Best mattress support: MDF, plywood, or metal springs?

[lt09]

I am considering three cribs with three different types of mattress supports: one is fiberboard attached to metal springs, one is plywood (E1 standard), and one has metal springs.

In terms of stability and safety, which is considered superior: metal springs or a solid board?

Thanks for any advice!

[Raewyn]

I went with a foam mattress so I could lift it - 8 lbs versus 30 for traditional coil.

But I am sure someone has an answer!