you are shooting at F/4.5 and F/5.6, indoors. both lens should be performing quite similar because you already stopped down ( using smaller aperture ).
The reason Sigma is a superior lens and is more expensive is because it is able to OPEN to F2.8. The reason you buy this lens is because you want to use larger aperture to create better bokeh.
And that to me, is a lot of difference.
LOL! Nice one guys. Who is playing as "L"?
The rest of the gang went Marina Sq.
Oh, I look so fat