daurelie,
I've always thought of inchoate as being more 'archetypal', whereas incipient seems more everyday.
Which I think is agreeing with shanks.

I too found that the difference wasn't as clearcut in the dictionary definitions, although 'formless' and 'formed' (but not quite in existence) sums it up quite well.

Sure I've also seen the words used as follows:
inchoate = "incapable of expression"
incipient = "about to be expressed"

So you could actually talk of a dumbfounded person being inchoate.

But I may have imagined this!

Fisk