Which is more low noise, open grid or open base?

After some preliminary listening test comparison between Pleiades V6 1H4 and Pleiades Siemens AC151 both are impresively low noise. When connecting the Shure VP64 microphone the transistor gives more gain and voice edge, it seems to overload easier when fed from Pleiades V6 1H4 as Vc is 1.5V. The electron tube is so smooth, quiet. How JFET would compare, open gate? Do radio telescopes use such low noise amplifiers as front end in order to detect few photons from the beginning of the univese?