Tough one.
For my cocktail, I chose identical "classic controls" with a 4-way and two buttons at either of the narrow ends. So, for stuff like MsPac, Frogger or DK, they come up in full vertical glory and flip for competitive action.
On one long side, I put two sets of side-by-side "standard fighter controls", each with an 8-way and six buttons.
My mandate with this machine was keep it really, really simple and, since I have a trackball on my Multi-Jamma cab, not include either a trackball nor a spinner.
If I wanted to play trackball or spinner games, the location would likely be determined by the native orientation of the games I wanted to play (which I guess would be vertical, so I could add a trackball to one of my "classic" panels and a spinner to the other ... or I could add them on the 4th side with a horizontal orientation).
Now that I write this, I find myself yearing for those controls for some cocktail Arkanoid and Centipede goodness ...
Cheers,
JAKD