I don't even know how to exactly describe my reasoning, but it's just kinda.. I don't like the idea of Batman, this dark brooding hero, having the same suit color in his cowl and cape as boyscout Captain America and Superman. When I think of superheroes with a blue suit, I think of Cap and Superman and they're pretty much the opposite of what Batman is in some ways. There's some color theory there going on that I can't explain.
I just associate the blue far too much with the idea of a "boyscout superhero" nowadays and if this film is going to dive deep into the more complex aspects of the character, him looking like a modernized West is just not my cup of tea. There's something about the whole concept of a black and grey Batman, with medium sized ears, with an imposing physique brooding that just sells the "troubled soul with a lot of darkness in his being" idea better than the grey and blue and skinny.
It can work, it can absolutely work because I've seen it work in some recent fanart but I feel you need someone imposing to sell it off and maybe Pattinson will get there but if they're reaaaally going to start this January then I can't really see that going over too well; maybe I'm wrong and I'll be the tiny minority that dislikes it or maybe I'll like it and I'll have to change my opinion, but based on the comments I've seen outside of these forums and the people that have been following this movie hardcore I don't think it will. People that don't have any connection whatsoever with the 70s Batman comics aren't too fond of the blue, they seem to associate Batman more with black.