For towing and DD, LML all the way. Not sure where these 20+ mpg figures come from, but expect 16. And if you tow heavy, 15,000 + expect 6-7mpg. The frame and suspension design is far superior to the LMM and older.
If you're looking for a fun/fast race truck.... I've always said the LB7 is king in that department. I've owned all generations, I still have my LB7:thumb:. It's by far the funest and most responsive/easy to tune for mods.