Really intresting thread this one, Im quite new to the site but have been lurking for a while. I currently drive a few different scrapers all moving coal, so we self load and only use the Dozers (D8L and D9R which I also operate) when we are stuck! Currently we have 4 Terex TS40's which have a 32 cu yrd bowls, these are the best for coal handling due to the shape of the bowl and the ejector. The are just uncomfortable after a couple of hours!
We also have 2 637 series2E and a 637E which have greedy boards fitted to the bowl so have a greater capacity, though off the top of my head I cant remember what it is.
I think my favorite is the series 2, but all are good.
Cheers
Matt