If you look at rampart (dedicated) the CPs have the buttons on the left and TB on the right. The Cabal kit ops manual suggests having buttons on both sides, and if on only one side then suggests to put the buttons left / TB right. Then there's missile command (buttons left, TB right) & Atari Football (select button left / TB right for 2 player).
Personally, I usually use my right to control the TB, except when going down right, where my left hand is faster. I'm talking marble madness & cabal, mostly.
So my dual TB CP has two buttons on the left of the TBs, but my single TB CP has three buttons on both sides of the TB.