What time of year are you going? FYI, the North rim is closed much of the year because it's at a higher elevation than the South rim. I suppose they don't want too many people slipping on ice and falling into the canyon.
The new "glass-bottom" overlook is on the north side, if that interests you.
I don't think you can go wrong either way. Flying into Phoenix and making your way north through Sedona, Oak Creek Canyon, Painted Desert, etc. to the Desert View entrance is spectacular.
Heading south from Vegas gives you many options, too, including Zion and Bryce. My personal wish-list item also includes Antelope Canyon, where you can see slot canyons, which look out of this world. You have to make reservations in advance with an Indian guide.