I think you're effectively talking about the difference between an API and an SDK. enTourage (at least to begin with would (I imagine) program against the API). I see an SDK as a more user friendly wrapper for the API so the development community can produce apps quickly without having to worry too much about low level API stuff and the nitty gritty of the specific device. Especially if the SDK is to be generic for the pocket device too. The SDK would probably be able to abstract and therefore hide minor differences in the hardware between the two devices.

That of course is just my opinion.

I don't think holding back on releasing the eDGe until they had an SDK ready would have been a wise move for enTourage. Having seen the CES2010 demos of various products on YouTube and held out till May for the Adam, the reason I bought the eDGe vs the NI Adam was that it was actually available.

Many of the other tablets etc turned out to be vaporware or were canned.