I think that with modern engines and modern oils there is enough margin for error built into the products that a given engine under a given set of operating conditions can get equally good results with a very broad range of oils.
I have noticed that in Europe, at least NW Europe, the oils available for purchase run very heavily towards very expensive synthetic products with much higher viscosities than we normally use in the US, and also broader viscosity ranges. If you were to commonly start a cold engine and almost immediately find yourself driving at 80-100mph (on a small high-revving engine no less, or a small diesel engine) on an expressway, I suppose that would be a good choice.
On the other hand here in the US we can justify almost any oil choice. We certainly see excellent results for very light weight oils right here on BITOG in the analysis forums, even on small, hard-driven engines. Yet at the opposite end of the spectrum some guys run fairly heavy oils and post equally good results. No doubt efficiency concerns factor into our lighter oils, as do driving conditions that are somewhat friendlier to the oil, but if there is no apparent penalty in engine wear then it is a useful savings that comes at no cost and I can't think of a good reason to find fault.
I suppose the conclusion should be that while there may be some benefit from attempting to "optimize" your oil choice for your particular driving conditions, it will probably make virtually no difference to the actual results and will in fact be one of the least important maintenance or service decisions you will make.
