Why is there any more "ease of changing ratios in a 9"? You have to set up both ratios to start with for either axle. Set up the 2nd ratio for the Dana as well. Then keep the shim packs and bearings on the spool. Either axle requires removal of brakes, axles driveshaft, and fluid drain. Then its either install a prebuilt $1500+ spare carrier in the 9". Or pull the bearing caps, pop out the spool, remove the yoke and pinion and install the previously set-up ring and pinion. Less than 1/2 the cost in parts. At worst you may have to swap the pinion shim behind the race. I'll bet there isn't 30 minutes difference max. I'm not against using a 9". But in most cases the cost is far greater for not a whole lot extra benefit.
Doug