Some brands are definitely better than others. Denso, Remy, Hitachi, Bosch, Nippendenso and more are just a few quality brands. You didn’t include the year, make and model of your vehicle so I can’t say which one I would recommend for you specific car. I will say cheaper is generally a really good indicator of quality in the auto parts arena.
Efficiency is affected by resistance in all electrical systems. The idea of efficiency must be taken into context of the action that the electrical component is designed to do. In the context of an alternator, output simply needs to output enough to current to meet the needs of the vehicle. The details surrounding this can be complex, so I won’t go into them. Not to mention, reliability of cheaper units are definitely not as good as more expensive brands. Reliability is paramount to efficiency in the alternator world and efficiency is fixed in such an electrical generation system. Again, this is a complex discussion, so I wouldn’t worry about alternator efficiency, buy based on reliability.
If the resistance you are speaking of is because of bad connections at the battery or other connections, these connections should be cleaned and the surface should be cleaned with sand paper. This will give electricity what it desires to flow more easily. Bad connections increase resistance and this causes other problems the affect the efficiency of the power system as a whole.
If you need an alternator, I recommend booking an appointment with one of your fine technicians and they can provide you with a quality unit. I recommend the following inspection to help you out. Alternator replacement
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