well, there are several i would consider. but I think It would end up being my 4" 629 out of the handguns I have right now. My reasoning is, it is very accurate, 6 rounds doesn't bother me, You can down load it to powder puff loads, or It can be loaded hot and heavy for a handgun if necessary, even though it shouldn't be done much. I am quick with it and you can slick up the trigger/action and be even faster. It is concealable believe it or not, and its light enough to pack around. It can be shot double or single action. And it is weather resistant stainless steel. You can even put a mount and scope on if you wish. It is also very reliable.
my Runners up are these;
5" half under lug 500 S&W. Has most of the advantages above, but while John Ross might manage to conceal his, I haven't found a way yet. And the darn thing is still heavy, even in that configuration.
EAA 10mm match elite. Has 15 round capacity, and all the rest of the perks, but no where close to as powerful as a 44 mag can go, or as light either(I can cast REALLY light bullets in 44). Your load variations are somewhat limited to what will cycle the gun.
1911 460 Rowland Conversion. It has most of the perks, but again, the loads are limited.
Encore pistol; Has everything except capacity.