So we've been continually linked with this guy for the past couple days, sounds like he's pretty keen to come and it seems like we'd be able to get him for around 25m, maybe a bit more. Hazard is better and younger but he doesn't want to leave in January, plus with virtually all the elite clubs are in for him he's much more likely to go to them than Chelsea, who aren't at that level, so Willian is a much safer bet. Plus, he's a pretty damn good player himself and would improve us for sure.
Personally I'd probably be inclined to get Willian now, despite him being cup-tied, since I just don't see Hazard picking us over Real Madrid, Barca or United in the summer. Milan would be smart to go for him as well. Barca would probably be the least likely to go for him though since I don't see where he'd fit into the side right now. But waiting until the summer and trying to outdo the clubs I just mentioned is just way too risky, and by the time the bidding war is over Willian could be gone too.