I'm orginal/subbie. I only watch Dragonball Z on the International Channel. I refuse to watch that poor excuse of a dub that CN airs. I buy the movie DVD's and watch the Japanese versions with subtitles. To me the main thing is dialouge. The Japanese dialouge is superior in nearly every aspect. The problem is Dragonball was aimed toward the 12 and up crowd in Japan(about 13 and up here). FUNi dummied it down so it would hold the attention of the average 7 year old. But the problem is the Japanese are more mature. Americans are sheltered generally until they are 18. And then there is the stereotype that cartoons are for kids. Yet when one shows blood or something everyone goes crazy and say kids shouldn't be watching that sort of stuff. Go figure.
Another big thing for me is name changes. Pointless name changes. Just because Kuririn is pronounced close to 'Krillin' doesn't mean it has to be spelled like that. It's more like 'Kulilin' anyway. And other stuff like "Tienshinhan". They could have said Tenshinhan. Pikkon is another stupid one. Paikuhan is perfectly fine for a VA to say. And it isn't like the names are hard to say or remember(children can after all remember all 251+ Pokémon.) There are others like Burter( instead of Butta or Burta), Frieza(instead of Freeza or Freezer), Cooler(Instead of Coola).
Lastly corny jokes, horrible music, poor VA's all really ruin the experience for me. That's why I prefer the Original w/ or w/o subtitles.