I think the standard cover is superior here, but I really liked the special edition cover for Volo's Guide to Monsters. The special edition cover for XGtE reminds me too much of Modern Art, which I find terrifying.
Easily the standard cover for me. I just can't get into the Special Edition cover. I'm still trying to wrap my head around it and that's why I think it's a bad cover.
At first I was sad that Volo's Guide to Monsters variant cover looked so different from the regular covers. But now that the "Guide to" is a series, I'm totally happy with them having their own design scheme.