Terminal 2 at DUB (which Aer Lingus uses) is much smaller than YYZ so, depending upon which gates are used, it is likely that your walking in Dublin will be less than in Toronto. T2 is a nice modern facility and I enjoy transferring there.
Having said that, I find AC in Business is a good airline - I've not tried Aer Lingus, but I gather that they don't yet have many seats that are lie-flat.