For the past few years Lie Nielsen, Veritas and others have been offering scrapers that are much, much harder than the traditional ones, which approximated to the moderate hardness you'd find in a typical western traditional handsaw.
I've tried both, and after an initial burst of enthusiasm for the new ultra-hard scrapers I find myself drifting back to the traditional ones. The new style need more effort to prepare, ideally with a carbide rod as a burnisher and a course diamond stone to remove the old hook rather than a file. Yes, they do last longer, but I'm not convinced that they cut quite as finely (although this could be a by product of the more difficult preparation).
There's also now a much greater variation in available scraper thickness, which presents woodworkers with yet another set of decisions!
It's not a hard and fast rule, but I find myself tending to use thicker, harder scrapers for heavier work and when the scraper is secured in a holder (such as the basic Veritas holder), and thinner, softer scrapers hand-held for delicate tasks (such as flattening stringing and inlay).
I learned how to use a scraper from Bruce Luckhurst, who emphasised a great range of scraper preparation depending on the task in hand. One technique of his that I regularly use is to prepare a traditional scraper with the lightest imaginable single stroke of the burnisher. It seems impossible that this single delicate stroke could possibly turn a hook, but that's exactly what it does, and furthermore it's the perfect hook for levelling inlay (which unfortunately is sometimes "spongy" and difficult to flatten without tear-out).
