There is no best; they are all good cameras. Choosing one over another comes down to preference. Look through the viewfinder. press the buttons, move the dials and knobs. You should choose one based on how it feels in your hands and on which one has controls that you find easy to find and use when you step beyond Auto mode.
SONY alpha A580
CANON EOS 600D (t3i)
I m confused between these 3 cameras.
Which is the best camera..?