I think you may be right in some cases, i.e.: some nutter on PCP but a normal junkie prowling your yard... look, being unable to see and breathe are absolutes. It's not like a 9mm through and through the thigh and unless it hits an artery adrenaline might get you out of there. Cannot see, cannot breathe? You are not going anywhere fast.
Don't underestimate what adrenaline and drugs can do. Attackers normally work in multiples. Your gas pistol will be useless. For proper home defence you need to firstly secure the perimeter, and create multiple redundant early warning systems. You need a side arm nearby in case these don't work, but for best home defence your weapon of choice should be a shotgun. Nothing scares the living **** out of an attacker like that. You point it, and shoot it. You wont need to worry about a 10mm slug going through your neighbours wall. If all you have is a side arm, you're not going to just let off one round. If you're trained you'd shoot off bursts of three or five and you'll have 15 chances to stop the threat. So, in short, for EDC, Glock 19 (unchambered first round - but one needs to practise drawing and racking as one motion), and for home a pump action of your choice.
And for a zombie apocalypse, nothing beats a decent vantage point and powerful rifle.
But get the pepper gun, they're good fun to play with. Shooting is fun.