Is stainless steel the same strength as silicon bronze? Which is more corrosion resistant? What options should I specify or consider?

The chainplates I have now are stainless and run outside the the liftlines along the outside of the hull. They are showing signs of rust stains down the hull, so I figure to replace them.

The plates are backed on the interior and all are accessible, although I don't plan on doing this myself... I plan on doing this in a yard along with a bottom job and replacing a couple of thru hulls.