2005 ram 2500 4x4 quad vs. 2006 ram 1500 quad 4x4

2500, may have fold out towing mirrors, 1500 probably doesnt. Worth getting for either one though. 2500 has a solid front axle, will ride like a TRUCK, 1500 is IFS, much better ride, if that's a concern.
05 style dash is known to crack especially if it spent alot of time outside in the South, 06- up doesnt have that problem.
06 Headlights are better, but not much. They both suck but are easily remedied with some better bulbs.