First off, the atmosphere is just not there. The 1967 film had black and white photography and a truly inspired score that really put you in the mood, and in the time and place. As usual in films that try to take you back to more innocent times - in this case rural 1959 Kansas - they get the art direction and costumes down and just get the personalities of the people all wrong. In reality, Dick Hickock and Perry Smith were just inches from turning on each other like wolves many times after the crime. Here they tussle a little, but the real dark differences between them are just not shown. Hickock was in actuality the stronger and the more sociopathic of the two, here he is shown as just a carefree womanizer with a criminal bent for theft. Likewise, the actual deep remorse that Perry Smith felt over the murders is not shown, nor is the fact that he was the weaker of the pair, and a dreamer. In fact, Perry is shown as the stronger of the two.
Not only are the criminals shown as not that menacing, the townspeople are shown as more modern in their speech patterns than was actually true. In a town where it really was true that EVERYBODY went to church every Sunday, where it really was true that a romance between a Catholic and a Methodist was doomed to failure, the female owner of the local diner is not going to yell across the room to a man who is a stranger to her "You bet your butt I do!" in response to how good a cup of coffee she makes.
Of course at the end, the details of the crime are shown - at least from Perry Smith's viewpoint - because today people are used to seeing that kind of thing in the news and on broadcast TV - a family killed by complete strangers. In the 1967 film the details of the grisly murders would have been out of the question since the production code was technically in force for another couple of years.
If you get a chance to see the 1967 version, it's a toss-up as to whether or not this one is worth your time. It is not bad, it is just not up to the standards of the original theatrical film.