We are installing new kitchen sink. Large tub on left, small tub on right.

Which side should the garage disposal be installed on?

If have space below the large side,there.
That's where you'll probably have dishes with food, and need run the disposer.

Ken

It is strictly a matter of choice but sometimes it is determined by the plumping under the sink, sometimes the plumbing will be in the way on one side but will fit OK on the other.