I've been meaning to get up pictures and an explanation of different boning types ever since I first got the spiral steel a couple weeks ago. I'm definitely liking the spiral steel, particularly for the boning channels at my sides. I haven't used any curved boning channels, so the side-to-side flexibility hasn't been too much of an issue, but with blush dupioni corset, both the duct strapping and the flat spring steel bones at the sides got permanent kinks in them after a bit of wearing. (I can iron them flat again, but it's preferable that they not to that to begin with. I'm also not sure how the bending and unbending will affect the life of the bones.) I used the regular (thinner) flat steel on either side of the grommets, and a thicker white steel bone the next seam over. I might have used the thicker ones for the sides of the boning channels, but I didn't have many of the thicker ones. The lighter weight bones do seem a bit too thin for stabilizing the lacing, but so far it hasn't caused any problems; we'll see if that changes with extensive wear. I didn't use any duct strapping in my denim corset. The duct strapping isn't bad, but is definitely softer and more flexible than steel or cable ties, and more reactive to body heat. It's significantly thinner than the cable ties, though, and also quite easy to sew through. I haven't actually used the plastic meant-to-be-boning boning at all. I got way back, before I did the duct strapping thing.
My preference for corsets is definitely a combination of flat and spiral steel. For other boned bodicies or anything else that needed a bit of extra structure, duct strapping is excellent, though. While it seems too flimsy for corsets, it's easy to cut, doesn't upset my machine to sew through it, and isn't too thick; it's actually very versatile.