A bit late on this one. One needs to consider length, overall length vs barrel length, width, weight, height, grip length.
To be legal in Canada the major consideration asides from the evil list and the evil calibres is the barrel length. So, if one chooses a handgun with the smallest amount of metal BEHIND that barrel, one is choosing the SHORTEST handgun.
However, after many months of playing I have still yet to come up with a decision on what is the smallest handgun suitable for my purposes, legal in Canada.
My votes would have to go to the H&K P7series (P7M8 and P7PSP) which are both outstanding handguns, deadly accurate with somewhat less muzzle flip, etc., than most others due to fixed barrel and inline gas discharge recoil assembly (piston). It is only in 9mm mind you, but the latest tests have shown that there is not much difference between effectiveness in stopping bears, etc., with a 9mm or .45 using 'engineered' rounds. One needs to move up to .44 magnum and that ilk in order to see a significant improvement in effectiveness, with that 44 magnum being a real humdinger in terms of wound channel and energy transfer. Dirty Harry had it right.
I happen to like the smaller calibres: 9mm, .40 and .45 and there is not a huge difference between them regardless of the old wives' tales that continue to float around (when using engineered rounds like Gold Dots or Federal Hydra Shocks, etc.)
And if you are thinking in terms of small, then you need to be thinking of the H&K P7's. We own two P7M8's and they are lovely guns. Also own two P7PSP's and they too are nice. Only issue is the price I guess. The P7M8's run at around $2,000 and spare magazines at about $80 each.