I use two wheeled trailers for the balance of things. When I'm hauling groceries or other things, I mostly only worry about front/rear load balance on the axle of the trailer as to not put too much load on the bike. I have a dual kickstand setup on my bike and often a kid, so not having my trailer being a tip over liability is also great.

I also have a lot of bikes I like to ride, so I prefer the clamp on style trailer hitch-up around the chainstays. This way I don't have to unbolt anything to put the trailer on another bike and the lower center of gravity helps keep the balance of the bike. If you've ever hauled a 5 year old on a trailer bike, you really notice if they shift around. Here is a nice load to the bottle club for me...there are also a bag of tomatoes for a niece under there and a customer's kid bike on there, you can see a hint of the rear wheel...might as well trip save.