From the top of my head, it’s Dragon ball Z. Here’s why,
Short and awesome: The plot of Naruto is more complex and heart-warming but it has loads of fillers, especially in the first season, the 220 episode one. The 100-175 episodes or so contains mostly fillers if I remember correctly. Meanwhile almost every saga in DbZ is comprised of pure awesomeness.
Rage mode: Rage can be converted to a super-power in dbz whereas it is seen as a comparatively negative effect in naruto. Sure, it gives him the power of the nine-tails but it deteriorates his body unless he gives up rage and takes control of it. In dbz, if you’re angry and powerful bham! you turn into a super-saiyan. This aspect is very captivating.
League difference: In dbz, if you’re the most powerful in the saga, you are at a different league from others. Like gohan in cell saga and Goku in the others. Naruto is at a different league in some fights but in most he has a more powerful or equally powerful ally. Best vs. The best is more addicting.
Looks cooler: No-one in Naruto has muscles even remotely close to the Z-Fighters. And let’s face it teen gohan Super Saiyan 2 looked better than anyone else in both series put together.
Legacy: Naruto, one-piece, Bleach, etc are the cool new kids, with different fan clubs, but dbz is the master, the legend, everybody loves dbz.