I totally understand your point. I don't think I could tell one from the other if blindfolded.
I recently fixed a Mavic Ksyrium Elites rear wheel for a friend. I had been warned by a pro wheelbuilder friend to keep away from such wheels but I'm the type of person that I enjoy a challenge and I wanted to know by myself why I should keep away. I had an idea beforehand of why wheelbuilders don't like fixing / rebuilding these wheels and that it is to do with the time is needed to do a good job. Time is money and I thought these wheels would require more time than other wheels.
My first impression of the wheel was good and solid. Not as light as I had anticipated. Closer inspection confirmed what I had already known about these wheels, every single component of this wheel could not be got off the shelve from my LBS if I wanted to. You can order everything at a premium cost if you want to.
Now, non of the spoke keys I have would fit the nipples, so I needed to buy a spoke key for the Mavic Ksyrium Elites and they do them before and after 2005. £13 for a spoke key that can only be used with some Mavic wheels, not all.
The secret of wheelbuilders for not ending with egg shaped wheels is keeping all things equal. Well, at that moment I realised that these nipples are not well suited for handbuild. The way the key fits the nipple makes things more difficult to try to turn each nipple an equal amount. Conclusion, I now know for sure why wheelbuilders don't like these Mavic Ksyrium Elites factory wheels :-) at a guess I reckon it takes twice as long to build and since time is money for wheelbuilders they hate them
I hated it too and I don't charge a penny
I have never told anybody that a set of handbuilt wheels would make riders go faster. I don't know any serious wheelbuilder that claims that either. That is something that riders claim but I feel it has been attributed to wheelbuilders on this thread.
In my personal experience I found that lighter wheels make it easier to climb hills. That has nothing to do with being handbuilt or factory built. I also say that bladed spokes would only make a difference at speeds of over 25pmh.
The advantage of handbuild wheels is in the durability and the easy of maintenance. If I have an accident and bend the rim I can get a replacement rim almost anywhere, something that factory wheels cannot promise. I'm talking about decent factory wheels. Cheap factory wheels have other issues that there is no point going on about here.