Not really an issue with the batteries and the Cannons as you will be recharging more than you will use, that is, if your engine is running while you are using them. I do like the controlled decent of the electric feed on the Cannons. You can also release the clutch on the Cannons anbd let the ball fall unassisted if you prefer that.
I think they are both good downriggers and i would go more on price than brand. The one thing I don't like about the Scottys is the mounting system with that one holed plate, but maybe the downriggers mount to it more solidly than my shrimp pot puller does. It waggles back and forth as the boat rocks since there is only one point of lockdown to the plate.
I know the plate with the horizontal hole in it has four mounting bolts... it is how the downrigger mounts to that plate that bothers me. My pot puller attaches with one cross bolt and rocks back and forth on that pivot point. I have never fished with Scottys so I don't know for sure if it is an issue with the downrigger mounting.
On a side note, I recently discovered that Cannon's lifetime warrantee only applies to the boom, spool, and frame, not the motor or power cords or switch covers that "lifetime warrantee" would implie.

The downrigger mount has a four bolt design. Very solid.
Her's the mount I'm talking about.