*Buzz*...Wrong-o buddy. The characters were created by Akira Toriyama. The only true-ness to the character is what Toriyama writes down. He did not choose Horikawa as Vegeta. A director did. Just because this director came from Japan and worked on the series doesn't mean he has a more legit opinion on how a character should sound. How a character should sound is subjective. Original does not mean true or correct. It just means he was the first.
If you are watching the anime of Dragon Ball, you are watching a product created by Toei (based on the story of Akira Toriyama), and therefore when it comes to the anime of Dragon Ball the characters become their characters (not Funimation's), and therefore the decisions on how characters should sound are theirs (not Funimation's). You don't like the adaptation Toei did of the original manga and how they brought some of the characters to life? Well, too bad. Still, that doesn't give Funimation the right to "improve" anything. Appearently now dubbing companies have the right to completely change a character if they think the way the original sounds is not appropriate? Are we crazy?
And indeed my example is like yours. You said voicing a character is very subjective and that Gokuh could very well have had a different voice. Of course. If he had had a different voice, then that's the way he should sound (or at least act and emote) when being dubbed to another language. And Vegeta could have been a different character, and that's they way he should be in the English dub. So what? Thing is, it happens that Gokuh has Nozawa's voice, and Vegeta has Horikawa's voice, and Vegeta is how he is. Speculating how they could have sound if, if, if, if, if whatever is absurd. They sound the way they sound. Period. And that's how they should be portrayed. It's not Funimation's work to analyse if the characters have been adapted accuarately. Besides, do you actually think that's the reason why all the freakin' characters in the dub sound different? The only reason Vegeta and Piccolo sound like that in the dub is they didn't want poor little kids to get confused. Having a bad guy sounding like a perfectly normal person? A green alien with a human, natural voice? They wouldn't understand!
One more thing. Using your logic, if the anime of Dragon Ball were a completely original series (not based on a manga), then Sabat's Vegeta would be intolerable because Vegeta would have been originally created by Toei? Then butchering characters of a series/movie based on a comic/book is acceptable because they are not actually their characters?