I think the more slightly more menacing look could work well if Hellboy's personality isn't too edgy. The endearing contrast between Hellboy's demonic appearance and rather human mannerisms is always the first thing about the character that sticks out in my mind.
Like, normal people are supposed to find him frightening until they get to know him.
I hope most of the movie goes as practical as possible. Its Neil Marshall in the director's seat and he's great at keeping the effects pulpy and practical so I have no doubt even on a tighter budget this movie is going to look great. Dog Soldiers was a treat and Doomsday while not having a great story or characters, was a great looking movie that did everything from Mad Max style chases to a Knights on horse back oh and zombies.
I'll echo what others have said; I would have LOVED to see how GDT wrapped up his take on the character. I respect that Mignola wanted Hellboy to end on his own terms even if GDT's vision wouldn't have conflicted with his own. Harbour is looking good here and I remain optimistic.
It's difficult for me if only because I have always respected Perlman's body of work and him playing Hellboy was some of the most inspired casting in comic book to movie adaptations I have ever seen. It's a hell of an act to follow.