You have lots of options, and it depends on your budget and how often you cook.
2006
We started loading everything into the back of a Suburban. Worked great, but took a long time to pack and unpack. That was fine because we were cooking 1-3 times a year, always locally.
2009
We then got a cheap used RV and pulled a cargo trailer with the bigger items like the smokers in it. In 2010 we built rolling shelves and started wheeling everything in and out of the trailer instead of carrying it from the RV - big time saver. In '09 used RVs were going for nothing because banks had stopped financing them for a couple of years. This was a lot less expensive than getting a better tow vehicle and a customer trailer, and having a shower, toilet, AC, and heat didn't hurt either. By this time we were doing 9-15 contests, so it made more sense for us.
2012 to the present
After 3 seasons with the RV/Trailer combo, my wife was convinced of the value of using an RV, so we replaced the older unit with a Toy Hauler RV so now we don't have to tow anything. We still use the wheeled shelving, too. Last year we cooked 19 contests, and some of them were across the country. We sometimes have up to 6 people cooking with us, so we like to set up outside - and this works well for quick setup and takedown.
Custom porch trailers, or toy hauler travel trailers (that you tow) are good options as well, the latter seems popular here in the northeast. Most toy hauler trailers are quite heavy, especially with full tanks, so the capacity of your tow vehicle is important. For me, I would have had to replace the tow vehicle, so the toy hauler trailer and a new truck vs. the toy hauler RV were kind of a wash cost wise.
If you are only doing a few comps, rent a cargo or flatbed trailer. Uhaul trailer rates are pretty reasonable, and there is no mileage charge on trailer rentals.
