I.m pretty sure i have only leaf springs in the two guns I own, a Greener 1901 pigeon hammmer, & a Belgian sle marked Britte on the locks.
I started shooting with a Beretta 686 O/U...what do they have?.
They all go bang...but I guess I like the hand made leaf just because it might have been harder to make,& sounds more traditional to me.
I guess a coil spring was hand made too, of course...just the V shape makes em so cool.
Or whichever lasts longest,lol..
cheers
franc