Each method has it's merits, and which you choose will depend on the body style you are using, your building approach and I suppose your temperament. Really, I could care less which way people attach a neck. It's not religion or politics, which I could care even less about as well.
In guitars I use a bolt on tenon for reasons of size, tension and more than anything else, customer expectations.
For ukes I go with the Spanish Heel, as it's what I discussed at length with Rick Turner when starting to teach classes. It's merits in the class setting so far outweigh any other method that it's hands down the only way I would do a class.
With that settled and my head wrapped around how to go about it in the class setting, I asked myself why I would use another method for my own instruments. And I couldn't think of one single overriding reason that would make me choose another. So I switched my production over to the Spanish Heel method.
Sure, it's a different way to build for many, and certainly those in the USA. And you do need some skill and know how to get it right. But thats not any more difficult that doing a good job in another method.
What it does allow is a very good neck to body join with no flossing or shimming to get the correct fit and pitch. You can use any shape of upper bout that you like. Mine is very slope shouldered, and is quite difficult to achieve with any other type of neck system. And if you were paying attention when glueing the neck to the top, the alignment of the fret board down the centre of the top is already dialled in for you.
For many, those three things are the most daunting and demanding aspects of building. The ones where the most things go wrong, and certainly the ones where it greatly affects the playability of the instrument, and ultimately its success.
The rest is just careful woodwork and experience.
