I once owned a 1500 cc v-twin motorcycle. The aftermarket oil filter was about 1/2 the price of the factory branded one. The factory filter had an anti-drain device which prevented the oil from draining down into the crankcase. This ensured that the engine still had lubricating oil throughout the next time it was started. The after market filter did not have this feature.
Not much relation to marine diesels, just wanted to show that there can be more than one way for filters to differ.
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40' Norman Cross trimaran