I think 2014 Godzilla will be scarier in the horror movie sense, just because as an audience we've gotten acclimated to films so much, it takes more to genuinely scare us.
That, and with the fear of the Cold War over, and our understanding of the workings of nuclear radiation more scientifically developed, it's harder to have the 'fear of the bomb' now than back then.
So 2014 Godzilla will probably be better at offering jump scares and building a sense of dread.
The 1954 Godzilla is probably a scarier monster to think about actually existing. The way it gave off radiation poisoning and how it seemed to be driven to destroy just to destroy, instead of behaving more like an animal like Godzilla 2014 will.
But yeah, it will be hard to get a verdict in until we see the movie.