30 fps is the standard frame rate for broadcast television (NTSC) in the U.S. (and Canada, Japan and a few other countries). 24 fps is what was used for movie theaters. (25 fps is standard for the PAL format used in much of the rest of the world.)
Might as well shoot in the frame rate that's native for where you live, unless you want a higher frame rate for slow motion or whatnot.
You need a balance that factors in motion blur. High frame rates are sharp, but the shutter speeds are so high they also produce a jittery, artificial look because there is no motion blur. That's the point of ND filters --- to get shutter speeds down lower to allow for some natural motion blur.