Whatever the level of remastering, they're going to look better than the DVD's, and for a tenner for three great films on a format that has far less compression, that's a bargain. Scenes within films can vary just as much as the films themselves - some scenes may be soft focus, washed out, different colour palette, or not even HD. Remastering can't really make up for this.
The comment about the DVD's having less grain - it might be that the 'noise' on the DVD's might have been reduced digitally - this clears up grain, but at the detriment of picture detail - in grain, there is detail. Also, there's usually confusion between noise and film grain. Noise appears every now and again when a scene is badly shot or the film has deteriorated - film grain is constant.