Getting new (used) 2nd Gen

Hi there,

Budget allows 2012-2013:

Main vehicle - mainly highway 20-30 miles daily.
Will not use this for offloading (have 98 for this purpose).
Occasionally will tow 24ft trailer loaded with hays (most of the time will use Dodge dually).
Louisiana weather - hardly snow but flooding is common. Need truck to be high.

Love to have 4WD like my 98. But maintenance $ is higher. I had to buy a new TRD diff for the 98 and it was more than truck.

Double Cab - check
V6 - check
manual or auto?
2 or 4WD - ?

Which would you go with? Thanks guys.