New SL1 vs M4/3s GH3
One's an entry level DSLR and the other is a $1600 m43 camera for semi-pro videographers. Kind of a silly comparison.
As for a debate between entry level DSLRs and entry level mirrorless, I suspect that's a pretty opinion focused subject. OVF or EVF? Very small size (until Canon cranks out some more pancakes and even then it is still bigger) or true PDAF? EF lenses or m43 ones?
I think mirrorless cameras are competitive with DSLRs. All that means is there's a perfectly big list of pros and cons on either side, and reasonable people would be perfectly in their rights to choose either.