Experiment
Used leeches on Lake Tapps for Small Mouth Bass.
Well I tried the leeches on a small jig head and fished them the same way as I fished a jig with plastic craw.
Leeches 0 fish caught
Plastic Craw 3 fish caught

Pluses
Much more lively in the water.

Minuses
The leeches kept tearing off the hook.
Had to be very gentle on the cast or leech would get hooked in the middle.
My fingers got cold from picking them out of the water filled container.
My wife hated the thought that they were in the boat.
As you can see I think this was a waste of fishing time and money.
Leeches not recomended for fishing for bass on the wet side of the hills.
Bill