I've never found the tape medium to be a factor for low light, sharpness or image quality. Those are more a factor of the lens (big = more light), the sensor and "the entire package."
AVCHD is pretty good but it's hard to get much traction today with Standard Definition content. Try watch some HD shots from the newer gear to get an idea.
i bought a Sony TRV-25 mini tape camcorder about (?) 8 years ago.