I read both VADTD novel vol.1 & 2 in English and vol.1 in French! I only have the digital books for the English version for now since tariffs are a hassle while I have the physical book for the French version (+ I got the pre-order campaign goodies lol)

I would say it would depend on a few things, including your preference concerning the covers' looks, you can search if you don't know but the English version is a mix of the different versions but it had the male leads' face on each cover while the French cover doesn't (it has the design of a romantasy book and it has sprayed edges).
Other factors are: prices (book pricce/shipping price), also the fact that the English version is one volume ahead compared to the French. And maybe in which language have you bought the manhwa version too!

About the translation, I would say both French and English versions are good!
The novel English version for the physical book is slightly different compared to Tapas' translation (most of it is identitcal but it has better translations for some stuff, if you want, you can compare the novel version in my tweet here: https://x.com/xomyseries/status/2010116733630075208 VS the Tapas web novel version in chapter 80)
The French version doesn't make a literal translation btw (it's better that way and it adapted to the French style), it's still very good (https://x.com/xomyseries/status/2034310077491105917 VS the Tapas web novel version in chapter 13)