Hey Roger
In real life it really doesnt matter. In the past 20 yrs I've had several dozen of both and they are both way stronger than any insert or adapter. I've killed an equal number of shafts stump shooting big rocks and iron deer, both usually just crinkle right behind the head and cant remember ever actually breaking one on anything. An early TBM article (early 90s) had the article on both and the hammer swaged was stronger but both were 2 or 3 times stronger than inserts. Now the sizes I use are 2016,2018,2020,2117,2216 and 2219 so they all have fairly thick shaft walls. I'm not sure if the thinner walls as as durable. I have thought about having a 5 degree chuck made and trying it myself but dont have the space to do it yet.........YMMV
John