The answer to your question is BOTH locations.
But specifically for the 12LA it is located next to the right hand side of the dash on a vertical column connected to the right loader mount. I use one and find it easy to reach and not in the way. I also use a Kubota B2910 and find the loader lever, which is located in the same place, to cause my right arm to be sore if I am in the seat operating it for more than a couple hours at a time.
On some of the larger TC series tractors (both D and DA versions) the loader control lever is located on the right rear fender, but those tractors don't use the 12LA, they use the 16, 17 . . .
By the way, the 12LA is a GREAT loader. I absolutely LOVE the visibility that you get with the curved arms and the sloped hood of the tractor. It beats EVERYTHING else on the market for ease of use.
If there is ONE thing I don't like about the loader it is the small control knob on the end of the control lever. It is a ball about 1.25" in diameter. I would prefer a larger ball on the end, but that is a very minor issue on such a well designed loader. My TC24D is my favorite tractor, and neighbors who play with FELs are very jealous of the sight line offered by the FEL.