Based on my experiences so far with trailers of three types (two custom built and one Bell kid's trailer converted to flatbed), vs various ways of mounting cargo on regular bikes, vs my CrazyBike2, I'd have to say that for really big loads (several hundred pounds), the trailers generally "feel" safer and allow better riding on teh bike itself, even when pulling a trailer behind CrazyBike2. The smaller wheeled the trailers are, the better they carry stuff, becuse their load platforms are lowered--if I simply lowered the load platforms they'd probably ride better with bigger wheels, but that's one experiment I haven't tried.
CB2 itself can haul up to at least 300lbs or so of cargo, plus rider/etc., but depending on how it's loaded it can be a beast to ride and it si VERY hard on the rear wheels (gone thru a lot of them because of unavoidable potholes and too much load and no suspension). Up to 80-100lbs or so of cargo, and it's not so bad, especially if a third of that is up in front of the seat, below my legs in the middle triangle. Would probably be even better if the battery itself was in the front triangle or mounted to either side of it, but I haven't ever made up a mounting for that test yet. But overall, it's not an ideal cargo-hauler because of weight distribution. It does ride better than any other bike I've had or tried, even when those are loaded down with only 50lbs of stuff, vs CB2's 100lbs, but I can't say that any of them were a good or fun ride.
I have seen so many cargo bikes of various types and imagined putting my loads on them (usually stacks of big bags of dog food, sometimes just large collections of Freecycled items), and most of them would probably either not survive that very well (either frames aren't made for the loads I need to carry, or they don't have suspension and the wheels would break on our roads), or they would probably wallow, or otherwise not ride well.
I have been considering partially copying something like the Bullitt or one of the similar designs, but as a semi-recumbent and with suspension to deal with the unavoidable potholes in traffic here, rather than breaking wheels on them when heavily loaded. But before I build it, I wonder if someone who has a motorized or motor-assisted one or access to one would be willing to load it up with at least 7 or 8 large (30-40lb) bags of dog food, and see how it rides in traffic on marginal to decent flat roads at 20MPH, including having to stop and start a lot. I havent' seen anyone around here with anything even remotely similar. Probably, I'll just have to build it and see what happens.