Hi Ed,
Well, here's where I show my ignorance...
I can only offer personal observation as I don't think I've ever heard or read why.
A thinner blade allows one to arc the blade, which in turn allows a smaller area than the width of the blade to be scraped. It's a trade-off. The wider the area the blade attempts to scrape, the more likely one will introduce chatter if too heavy a shaving is attempted.
A thick blade allows a wider contact area and I think it doesn't need sharpened/reshaped as often.
So, for me, a thinner blade is better for small areas, the bigger, thicker blade for larger surfaces.
This is how I use my scraper planes:
The thinner blade on my LV #80 a-like, unless I have it bowed, it cannot take a full shaving without chatter. It is not really made for prolonged, full-width scraping anyway. I use it more for scraping veneer in small areas or glue lines, etc.
My Stanley #12, with a thin blade cannot take a decent shaving, but with a Hock blade in it, it does a wonderful job. I use it for full veneered surfaces, but smaller ones and or thin veneer. I use it more "delicately" than I do the #112.
The LN #112 doesn't have the ability to bow a thin blade, nor would I think I would want to. I use it for work on either solid wood tops, panels, etc, or on shop-sawn thick veneer. It can take wonderful shavings off highly figured woods (as per Frank's picture).
The LV version of the #112 can accept both a thin blade, used bowed for localized scraping as well as a thick blade for full-width scraping as one would do over a large surface. For this reason, I would have most likely gotten the LV version if it had been available.
Mike