is this movie better than 'Vicki'?

By a huge margin.

It's ironic that, despite being slightly longer, 'Vicki' feels like a bad summarization of this one. Probably because Christopher is introduced in a rushed way and there's not enough focus on the relationships between the characters before the murder, but the writers added instead a lot of useless moments, mainly involving Cornell. There is no possible comparison in terms of rhythm, atmosphere and especially performance, as everyone here is better than his 1953 counterpart:

-In the second version, there's not enough contrast between Jeanne Crain's Jill and Jean Peters' Vicki: both are gorgeous in the extreme and you could have easily seen them switching roles. Also, possibly in order to downplay her natural glamour, Crain goes for a somewhat mundane acting style that further slows the rhythm. Grable, in a nice against type performance, is plainer than the bombshell Landis, but also very energetic and makes the relationship btw Jill and Frankie very entertaining.

- Victor Mature may not have been the most expressive actor in the world, but I find him an underrated performer, who occasionally gave remarkable performances (his best being 'Kiss of Death' IMO). Here he works well enough, displaying remarkable charisma and screen presence and his 'rocky' persona makes him an unique and nice match for Betty. Elliott Reid is simply pathetic in the new version. One of the most boring, wooden and inspid leading men I've ever seen.

- What turned me off more than anything else was Richard Boone trying to fill Laird Cregar's shoes, though. Seriously, I think this movie may have been more ordinary if it weren't for Cregar's characterization of Cornell, which is what makes it special. He's so subtly sadistic in it; the moment where he watches Vicki through the window or the one where he's sitting in front of Frankie when he wakes up are so genuinely disturbing just because of his brilliant, effortless acting. And the way he gives some feeling of twisted romanticism to his final scene.. pure genius. All these moments are totally insignificant with Boone in his place. His Cornell is a totally one-sided, granitic brute.

So, all in all, Laird's performance might be what really makes the difference, but the original is superior in every other possible regard.