The reason for the change was that the old keyboard was not comfortable any more after around two years of usage. I think that the old keyboard model (in general, not the specific one I had) developed problems after some months of intensive use: its keys lost the smooth pressure feeling they once had. (Maybe adding some kind of oil beneath them might fix this problem, though, as the keys can be easily detached from the keyboard.) Due to that, it was becoming extremely hard to type on that keyboard without mistakes. Plus I have lately got used to laptop-style keyboards: short and soft keys.
The new keyboard model feels nicely so far. It surely is basically a desktop-sized laptop keyboard, as its keys are very short and soft. But overall I like how I type on it, and my error ratio has lowered back to almost zero again :-) If you are dubious about buying this keyboard, give it a try!