I have shot the FN 57 a lot and while I like the gun (I like most guns) I don't believe it would make a good home defense gun. I have a farm that at one time used a lot of migrant farm workers and they have left among other things several old cars laying about and we have what we call a bone yard of junk. I wanted to preface that before stating the following. The 57 will shoot clear through two car doors with the windows rolled down. It will shoot through steal bumpers like they weren't even there and it will shatter a windshield no matter what angle you shoot at it. None of which a 45 auto or 9mm will do. All of this was done with aluminum core jacketed 27 grain bullets.
The pressures that the cartridges are loaded at and the way the action works makes the case life very short and some what dangerous if you try to get more than 2 loadings from a factory case. You cannot even begin to re-chamber a fired case as it looks nothing like it did before firing, causing the brass to "work harden" when resizing making it very brittle. The gun is well made, very noisy, fairly accurate and has very little recoil. In my opinion the only thing the gun is good for would be to defeat body armor or to have as a toy. As for a personal carry gun it would also be in my opinion very irresponsible to carry one for that purpose because the penetration is so great.