Having read around this subject for the last few years, I would sum up the main differences as revolving around the status of 'the observer'.
For Sartre the observer looks outwards and contemplates 'an external world' in all its often trivial detail of arbitrary value.
For Heidegger, the observer (Dasein/sense of 'self') is often absent, and 'reality' is about a seamless 'automatic coping'. It is only when 'self' consciously agrees to choose its 'path' that 'authentic living' results.
For Derrida, the status of the observer is nebulous and context specific. The 'self' which has just written this reply will no longer be that same self tomorrow, and nor will the 'meaning' of this text be the same to the author, or tomorrow's reader.
Obviously, given the iconoclasm inherent in these positions which all embody the issue of semantic shifting, any attempt at a definitive
'answer' to you would itself be problematic !