"But each to their own."
Indeed Brian. It was not my intention to detract from any of those performers, I think they all have their merits, and you would have to travel a long way to find somebody who has done as much for folk music as Martin Carthy. That said, I have been revisiting recordings of all these singers recently to see if my opinion has changed at all; I find it hasn't reeeealy.
I am convinced that they all approach the songs as pieces of music rather than narrative, which is not what I am looking for. Martin actually puts in extra sung syllables into much of his singing which I find extremely irritating, but as you rightly say, "each to their own."
"recite song verses as if conversing"
It's a great way of work. In our workshops while working with a singer we used often to stop them at the end of a verse and tell them to recite the next verse. When working on my own singing, the first half dozen times I worked through a new song I recited rather than singing it to familiarise myself with the phrasing.
It is quite difficult to sing every word as you say it, but it is possible to shift emphasis onto words that need stressing and thus utilise the tune - overstressing 'and' and 'the' and 'but' type words is a real turnoff for me.
The old Clare singer, Tom Lenihan summed it up when he said, "do it as near as you can". Four squaring used to be one of Ewan's early problems, though he worked on it quite extensivley. I really noticed it on his Manchester Angel - he breaks up the second word on the very first line 'co-ming so the first syllable sounds as if he's trying to be sick!
"Bill Cassidy, is working in the opposite direction to the conversational,"
Bill's way of singing is interesting - as you say, not conversational. I always thought that he had been influenced by the Sean Nós style, but I have found an interview we did with one of his relatives, 'Pop's' Johnny Connors who sang in a similar style, but not as skilfully. He explained that the family learned many of the tunes to their songs from grand-uncle Johnny Doran, the piper and the style some members of the family were lifted directly from that. Johnny gave us a long session describing how the piping technique influenced his singing.
As far as all the Travellers are concerned, talking about singing style was fascinating as so much of it was shaped by street singing and ballad selling. Mikeen McCarthy said that his family sang in three different ways; one for pub singing, one for ballad selling,("slow enough to make a song last as long as the street") and then that done around the caravans at night which he called 'fireside singing'.   
Richard Mellish;
"I have heard recordings of source singers where they stop for breath in an obviously wrong place,"
I think you are quite right to put this down to age and shortage of breath. If you want a classic example listen to Phil Tanner's recording of Banks of Sweet Primroses, which he makes a magnificent job of, until he comes to the last line of the last verse when he actually runs out of puff and takes a breath.
One of the best singers we recorded, blind Travelling woman Mary Delaney, always used to make us play back her recordings and she invariably got upset with herself and said "Damn the bloody fags and booze!"
If you want to hear a source singer singing like he speaks - listen to Sam Larner's Butter And Cheese and All where, on the penultimate line he sings "The dogs they barked, the children screamed, out flew the old women and all" - then he interrupts the narratibve by saying "And you know what they are, don't you" - which is totally seamless to the singing.
Getting carried away again - must go - Wallander's on telly.
Jim Carroll