Original has a better score overall, just due to having more variety. Also, post-Namek the original Kai score is totally removed due to plagiarism, so it just has Kikuchi pieces shoehorned in at short notice, which made it even worse from then onwards.
There are also bits of filler that added depth to Z, such as Gohan's training alone, the driving lessons, Krillin throwing a rock at Goku's head and fake Namek (fku, I will die on this hill). Garlic Jr was largely a waste of time, but it also gave us a chance to see Krillin etc in action again. I'm fairly certain there are a few story-enhancing embellishments added on Namek too, such as Goku having a vision of Vegeta.
All in all, I would recommend people to watch the Japanese original dub if they are willing to go through so many episodes (the pacing really didn't feel that bad first-time through when you don't know what's coming, until it got to Semi-Perfect Cell and again in parts of the Buu Saga where it was honestly irritating), but otherwise Kai isn't an awful choice either. Obviously there's plenty of enjoyment and value to be got from just watching the Funimation dub too, which was still good enough to pull in the vast majority of American and Canadian fans and is probably still impressive if you've never seen anime before (unless you just hate DBZ-esque stuff, in which case go watch Bridget Jones or something).
If I'm watching it myself any time soon, it's likely to be Kai, just to save time. But I don't watch Kai as its own series, more just as a homage to the original or as supplement to my existing connection to Dragon Ball, I guess you could say. If I have kids or something I might rewatch the original though.