Unless you have a parking or other constraint, your best bet is to keep the dually.
At 7900, your new trailer is pretty much out of the 1/2 ton range...(yes I know there are a few that can do it. But they are rare and expensive, even pre Covid) So I do not see a point in taking a bath just to step down to a 3/4-1 ton SRW.
Your dually will make a superb TV for that trailer, and since you already own it...The cost is not an issue. It will take a long time to make up the cost of changing vehicles with the small fuel savings you would get.