Diesel vs gas......................

I almost bought a diesel instead of my truck, heres the story. I saw a 2003 dodgeram 3500 quad cab full load ctd 160000km one owner for sale 19000.$ Drove down to the lot to look at it it was beautiful drove it wasnt to bad ,told them Id think about it and decided that night to go back and get it. When I arrived the next morning it was just being to delivered to the new owner not me DAMN!!! Anyhow the sales man was right I should of put a deposit down ,then he showed me a 2003 ram 2500 hemi quadcab full load 170000km drove it loved it was asking 19900 got it for 16000$taxes included. Cant say I really wanted the diesel but pressure from friends and family in regards to milage and towing and longevity led me to think I needed one. My current trailer is somewhere between 6-8000lbs loaded its a 1980 kustom koach bunkhouse 24ft havnt had the opputunity to tow with the new ram hemi cant wait. The old tv was a 1991 gmc 2500cab plus long box 350 v8 auto pulled it but slow 30 km on steep hills first gear. Thanks for all the answers and input .ROB