How close will Sigma 30mm f2.8 get me to SEL 35f1.8....75%, 85%, 95%, 99% ?

I am not in love with the kit PZ 16-50 on my NEX-6.  a little too slow at 30mm for low light situations and a PIA to have to zoom around every time a turn the camera on.

How close in IQ will the Sigma 30mm get me too the Sony SEL 35?  I'm not ready to drop nearly $500 on a lens (i.e. still suck).

Thanks