Which is more accurate: digital or vinyl?

64 bits? Bit depth describes the dynamic range, 16 bits=96 dB, 20 bits=120 dB, 24 bit=144 dB. The later could record a jet taking off and a pin drop without changing the gain. That's more than enough for the most dynamic music with headroom to spare.

How does a finer definition of amplitude equate to resolution? Would smoother amplitude levels be audible?

16 bits specifies 65,536 levels, approximately 0.00146 decibel per level. I've read conflicting accounts. What's the smallest level change the human ear is capable of discerning?