19.5's here and NEVER looking back! 4,500# each tire (14 ply) and my dually handles anything I throw at it like a boss!
My truck plows snow in the winter, and year round tows a 30' tri axle bumper pull 2-car trailer, which is 7k empty with empty tongue weight @ 1,000 lb. pulls it like a dream. I do run air bags in back that helps a ton too!
I wouldn't consider anything else.
Tires I run are TreadWright Guard Dog MT these are a high quality recap using a 14 ply Good Year carcass for stability and a light duty tire compound which gives excellent traction and improved ride (softer compound than virgin 19.5's would have). Tread pattern is identical to Good Year Wrangler MTR and they are AWESOME tires! They have excellent traction in any weather. Also just under $1,000 for all 6 to my door! They are 245/7019.5 which comes out to 33.5x9.5 basically.