There are smaller versions of the Leigh jig. They will work for up to 12 inch wide joints. They are far easier to use than the jig type (porter cable type), you have.
The jig you have requires very careful adjustments, and you will be moving the router over the edges of the workpieces. The newer jigs, (I have a Sommerfeld dovetail jig, similar to the smaller Leigh) hold the workpiece in place as you move the jig over a table mounted router. That is safer and requires less adjustment.
You will only need the large Leigh jig if you are making boxes (for example) where the sides are higher than 12 inches.
I personally don't have free cash to spend a thousand bucks on someting I might use once or twice in my lifetime, when a smaller jig would fine for all other dovetail joint sized I'd likely use. I would rather use the extra money to buy some other tool I might use all the time.
If you have the money, then the Pro, larger version is a nice thing to have around, and it will work for smaller joints as well. We here all love to spend other peoples' money, but this is your money and completely your choice.
The more I do, the less I accomplish.