I do prefer the variant cover, but I agree that the regular version is one of the best covers we had so far. With Volo's for me there was no doubt in getting the variant cover, this time I had an harder time deciding.
I think there are two elements at play here that I particularly like.
One is, of course, the fishbowl and the eye superposition. I think everyone can agree on that, it's quite well done, and original. We've all seen dragons breathing fire and giants looming over PCs before... but a beholder and his pet fish? Now that's cool.
The second, and more subtle, is the look on Xanathar's face. It's one of the most... almost poignant... beholder I've ever seen. On one hand, he definitely looks monstrous. On the other hand... it's this strange awkward smile. It's not so much a "I'm going to eat you hahaha" smile as a "I hope we can be friends but I'm shy and I'm not sure, this hasn't gone well before" type of smile.
I dislike beholders, in general, so neither one really wows me. Beholders are part of the D&D lore, though, and the standard cover is probably the best picture of one I can remember seeing. It looks like the same art style as my other D&D books and would feel like part of the set, on my shelf. The special edition, on the other hand, is a hideous mess. I just don't like that style of art.
Really, the name bothers me more than the art. Even putting aside the fact that it's yet another general book named for something in the Realms, "Xanathar" is one of those fantasy names that seems like someone with absolutely no "feel" for language tossed some letters into a blender. It's just missing a couple of apostrophes and it could be a punchline. Yes, D&D is filled with dumb, crappy names. Xanathar is just one of the worst.
In sum, all of the above is almost like someone at WotC ran an algorithm specifically to see what would turn me off in a cover and this is what it spit out. The special edition is what happens when they let it run recursively, overnight. This book will mark my first digital-only purchase on DDB, mainly because that's what lets me best ignore everything about the cover.