I use both...
Part of the Estate is open to the public, and when I used springs, I saw Joe Public walk up to a feeder, say "How does this work?" and wrench the spring to the point that the barrel emptied! So for the 'Public' areas, I use pans now. (We have Peafowl & Guinea Fowl in the public areas).
Those areas where the Fee-Paying-Public aren't allowed, where I rear pheasants,I use springs.