Protections against spikes in the design of AC and DC electronics?
I would suggest AC because odds are that the "engine" is powered through a transformer of sorts, thus removing your connection to your source of energy. Sure, if lightning strikes the "engine" everything connected to it will be destroyed, but the energy source won't be affected as long as there is proper grounding. The transformer should provide adequate isolation and providing the circuit with an easier path to ground should protect your "source". AC also has the added benefit of being way more efficient for driving electric motors ("engines").