I have both the new and old. What I wore yesterday was the new.
Purists on the perfume boards will have hysterics, but IMHO the new one isn't bad as far as reformulations go. I find a lot of the negativity overblown; or, if not that, maybe that when reviewers try things side by side it's hardly an objective comparison. They already love the original and have a negative impression of "corporate" parfumery... so like seeing a color transfer of their favorite B&W movie... sometimes they just go out of their way to hate it.
And, given the susceptibility of Diorella's all-important crisp top fruity/citrus notes to degrade in vintage juice, coupled with the ridiculous pricing of vintage, I'd just buy the new.
I don't hold this view with all reformulations, of course; Diorella now is definitely not the 2000 "reimagining" of L'interdit that was an entirely different scent. Nor is it the current thin, pissy water of Givenchy Gentleman where the old was thick, boozy, and rich. You'll see in the new Diorella all of what made the original fun, and also how it fits into the DNA of Roudnitska's scent development.
And, weirdly, most online discount retailers are charging more for it than Dior itself is doing (even on ebay it's usually $100+ for the same bottle; straight from Dior it's $98 with free shipping). I guess the aftermarket sellers are banking on the fact that some customers must not know it's currently in production?