I'd run the ARB in the rear for offroad or DD. But DD for sure nothing like a open diff on the pavement, and the front needs to be locked more on the trail. IMHO
Put it in the rear for nice daily-drivering, and twin-stick the Tcase so you can have 2WD Low range to release the front Detroit for steering ease offroad.
Or, deal with the Detroit on the street, and the ARB will be awesome in the front offroad. You already know how the Detroit behaves on the street--so you'll have to decide how much it matters to you.
If it is your daily driver, I would put the ARB in the rear. Especially if you are going to drive a lot of snowy roads and such.
I personally dont trust arb's enough to have one in the rear. Even on a daily driver. With the detroit in the rear you can count on it.