I knew someone would come in and say reliability. Thats one of those "Well Duh" answers. So I've edited my initial post, lets stick the responses provided and assume you have reliability.
I gotta go with handling. No matter how well it fits the other categories if you don't like the handling of it you won't carry it, won't shoot it, or if you do it won't be as effective.
since reliability is a given, handling! it could be the most accurate, concealable, biggest bore, gun there is, if it doesnt feel good in my hands(glock) im not going to be able shoot well with it. thus negating all those features.
Reliability is a feature and is not a "given" feature of all "carry intended" pistols...
But my vote was for handling... If it don't handle well, it won't even make a good club!
Brent
Accuracy in the traditional sense is fairly irrelevant in a SD gun. We're talking about hitting a person from a few feet away. A gun that shoots 5 inch circles at 7 yards is just as effective as one that shoots 2 inch circles.
Caliber is an interesting choice... if we're sticking with "typical" SD calibers it becomes less important.
Concealability is a matter of choice. Choose to conceal an AK and you can do it.
Mag Capacity is largely irrelevant, IMO
Speed is closely tied to caliber.
Weight could be a significant factor.
Price is an odd one. If the gun is already reliable then you must be paying for things like weight reduction or durability or maybe just the name on the side.
What is meant by "speed"? How quickly it can be shot? How quickly it can be reloaded? How quickly you can get it from holster to on target and shooting?