A firearm is definitely more effective (in the permanent sense), and a solid deterrent (which is why I carry). But don’t discount the effectiveness of pepper spray: with it, I can reach the holder of the pickaxe handle out of his effective range, and within 2 seconds he will be in extreme pain and virtually unable to see.
And within that 2 seconds he will have busted open you noggin like a ripe melon.
Pepper spray is cruel and unusual punishment. My method, if properly applied, is virtually painless to the perp. /sarc