There's a big difference. Adaptations are new works based on the original. The original work is still available to enjoy or critique in its original form.

However, these new editions are effectively replacing the old ones. I don't so much mind them rewriting the books so long as the originals continue to be published. However, I don't expect that will be the case. Eventually, anyone going to a bookshop to buy one of Dahl's books will struggle to find the original version. That's a real shame, I think.