I think it really depends, pawing through a field of water vs trying to float over a soft field. If you are able to float over the field and are trying minimize ruts go with duals, big duals 20.8x42 for sure. If your in extreme conditions where you going to be spinning up and down the field I would consider 76x50x32 floaters. Duals do a great job of floating, but if you start sinking and need traction & tread cleaning a floater would be better IMO. Duals would still be better than 30.5s in any circumstance.
If the 30.5 are r2 tread they would be better than the duals for bad mud they will leave a bad rut they slice through the mud 76 50 32 float tires work good for soft ground but if they spin your stuck we run a lot of rice and have very bad buckshot mud I would not have anything but 35.5 32 r2 tread tires