That completely depends on you. If you are a dueler at heart, then an RGB saber is the best. RGBs have a strong polycarbonate blade that can withstand hard impacts and long duels.
Neopixels, on the other hand, are better in terms of light and sound effects (you can even customise if you have a Proffie saber). However, to make these effects, Neopixel sabers use individually-addressed LED lights along the blade, which can be damaged if you duel too hard. But that doesn't mean you can't duel with them at all; you just need to tone it down a bit.
Hence, if you want overall vividness and an authentic experience, choose a Neopixel. And if you are an avid dueler, RGB is your best friend.