The OEM versions for different manufacturers are always at least slightly different, although sometimes the differences are not easily discernable. Differences could exist in positioning of internal components, tread pattern, materials, or other subtle variations.
The difference is usually not huge, but to the extent you have confidence in the BMW engineers, you may prefer to stick with the BMW spec version if possible. BMW's goals may not always match yours however, so if you find something else works better for you, that is fine.
The load ratings are secondary. As long as you have enough load rating for the vehicle, extra load rating does not help you. Unless you armored your vehicle or turned it into a limo or something, you probably would not use the extra load capacity. The original load rating already accounts for a fully loaded vehicle plus a safety margin.
Last edited by ben@tirerack; 09-03-2009 at 04:10 PM.