All other things being equal, I also vote for the Hemi as having the extra power won't cause any issues. But, if you needed to add it someday, it'd costs a bundle. Remember, the upgraded 4.7 engine was pretty new at that point while the Hemi had been around since 2004. With the Durango's 5000+ lbs to move, mpg difference will be minimal and the pricing should be similar Hemi or not.
At the end of the day, either engine should do a fine job for you so look for the best deal you can get in the color you want and go for it. From some quick research, it appears that both the 303 HP 4.7 engine and the older 235 HP 4.7 used the same VIN designation of N in the 8th digit so you'll want to make sure any 4.7 you look at is the "upgraded" double plug version like the Hemi. There was also a "Flex Fuel" 235 HP 4.7 version indicated by a P in the VIN. The early Hemi's were indicated by a D while the later ones used a 2 and then a T for 2009.
Hope this helps.