Oblivion had better voices overall, though Morrowind's voices had better distinction. The Nords had an accent in Morrowind (even though they were voiced by the same guy in Oblivion), the Khajiit sounded like felines, the High Elves snobbish, etc. The voices Oblivion had were improved (Elisabeth Noone did a much better job with the female beast voices and Wes Johnson really commanded as male Imperials; the addition of Ralph Cosham and Craig Sechler worked great for male Bretons and male Bosmer, too)... it just wasn't as diverse.
I will always remember the Khajiit lady in Balmora mage guild: “May you always walk on warm sand” the voice was wonderful.
However many years later I was at a beach in the tropic with black volcanic sand. First thing I thought about was her and understood it was not a nice thing to say.