Eureka and Hinata sound the same in the english dub because they're both played by Stephanie Sheh.
Anyway, my opinon is that dubbing anime is necessary in some cases. It is often much easier to enjoy more thought-provoking animes when you don't have to spent your time reading the screen. I like both dub and subtitled animes but I pretty much stay with one once I've started a series.
Animes like Eva, Cowboy Bebop, Samurai Champloo, and FLCL really had quite nice dubs, and there are really talented english voice actors out there if you'd take the time to follow their work. Take Johnny Young Bosch, he plays Ichigo in Bleach, but almost a completely different voice for Renton in Eureka 7. Then who could forget Steven Blum/David Lucas who played Spike in Cowboy Bebop, Onizuka in GTO; though his voice doesn't change as much from character to character, every performance I've heard him do (aside from those horrible Toonami ads) has been absolutely amazing.
There are exceptions like Naruto or DBZ where they completely butchered the casting of certain animes (mainly funamation's fault), but the english dubs of animes have gotten much much better and I usually prefer them to watching an anime subbed.