Not much. I liked 3 tenors way back. I’ve heard a few amazing voices. But, I don’t care much for the way they use vibrato in their voices all that much. But I’m super picky about voice vibrato.
Ok. Now you inspired me to find a video comparing vibratos.
This video shows slow, even and fast vibratos.
My conclusion? I don’t care what speed the vibrato is, but it shouldn’t be disruptive. Much of Opera encourages a choppy, obvious vibrato which I don’t care for. It’s like a repeating hammer to my ears.
But if it’s smooth vibrato, fast or slow, I like it.