From my experience with rotating equipment we have used both babbit and bronze sleeve bearings. Tin-based babbit is softer then bronze.
Both bearings should provide acceptable experience if exposed to saltwater if you use a tin-base babbit, and an aluminum nickel bronze bearing is used for exposure to salt water service. Is this question related to the potential of a seal to fail and sea water is introduced into the air or oil-cooled bearings?
The concern between these two types of bearings is lubrication and durability. Babbit is typically more forgiving in sleeve bearings because it can tolerate some level of debris in service, and it normally wipes before catastrophic failure. The babbit has a lower melting temperature in comparison to bronze so if you have thermocouples mounted in the bearing housings, you can prevent damage to the shaft should the babbit wipe in service. For bronze bearings, if you have any debris that can effect the oil film, the bronze bearings will fail quickly and result in damage to the shaft.
