You will get many different answers as it is largely personal preference, I have a 2006 and love the engine and overall somewhat simplicity, no traction control and fairly raw power with little torque management, easy to modify and play with, but the transmission , 48RE if you go auto, is less then ideal even built just too big of a range between gears, the interior and seats really suck compared to a 4th gen even with new set pads. The wind noise in cross winds coming in the top of the doors on 3rd gens is annoying, pretty noisy engine and interior.
If you want a fairly reliable truck the 06 is a good option but if you want something more refined then the 13+ is a better option especially for towing as the 6spd auto is much easier to tow with.
They all have pros and cons, I would drive multiple years and trim levels to decide what you want then look around for a clean well maintained truck.