I switched to a small fridge instead of a cooler, I love it. I have a super compact setup, just the little cargo area in the back, so I'm always trying to shed weight and loose bulk. You have more leeway of course with a trailer, but I still think a fridge is wonderful.
I don't have to worry about finding somewhere to get ice, my stuff isn't sopping wet, and it's so much lighter.
It's smaller but bigger, if you can wrap your mind around that. I used a 26qt cooler before and I usually had to fight to get it closed, but now a 18qt fridge seems like plenty, I actually throw extra stuff in sometimes to keep it full. It's because I don't have to take up space with ice. So get a fridge to fit your space, and know for that space, you are able to actually use all of it for your cold stuff, not your cold stuff + ice. Ice takes up a lot of space.
Another really cool thing about a fridge, is you can actually dig around in it and get stuff out of the bottom without making a big mess or freezing your hands, or busting ice. I mean you loose cold air that way, but it will recover unlike a cooler and once you let heat in, you loose that cooling capacity permanently. I also never trusted a cooler to keep my food at a safe temperature throughout. With my fridge, I set it to 32-34 usually, and it stays close to that as it cycles. I know everything in there is staying cold, not just whatever is floating in the cold water.
The big hurdle and cost is in keeping an ample and healthy power supply to it, in some cases I'd say that is more trouble than getting the fridge. On a trailer it will be slightly more difficult to set up than attached to the vehicle, but that also has it's own advantages.
