It really depends on the brand.
Bob makes really good cargo trailers that have the advantage of being a single-wheel design (Yak). They are narrower and have less drag. They are a staple for people who chose to ride cross country with a trailer. These last life-times, which is more than can be said of a kiddie trailer purchased at Walmart. But like all quality things, you pay for it.
Wike Bike (made in Canada) has a number of cargo trailers (including ones for canoes and kayaks - try fitting those in a kiddy trailer!). The most Mustachian of which is actually a build kit for a DIY cargo trailer. They supply the wheels and connections, you supply the aluminum square tubing and make it whatever size/length you need.
http://www.wicycle.com/cargo_diy_kit_bicycle_trailer.phpThey also have a heavy duty landscaping trailer intended for carrying lawn mowers and yard tools.
http://www.wicycle.com/cargo_park_pioneer_bicycle_trailer.phpProbably the biggest advantage of Bob, Wike, and also Chariot and Burly, as compared to the Big Box cheapy kiddie trailers is the availability of parts. If anything breaks on any of the above brands, I can go to the website and get a replacement part quickly and easily. I almost picked up a 10 year old Yak, and found that I could still get all the parts I would need to rebuild it. I have a friend with a CCM branded kiddie trailer, and he's SOL for a few parts he needs, so he has to kludge something together (Thankfully he's just using it for gorceries, so safety isn't a concern to him).
If your goal is groceries, then a kiddie trailer is sufficient. If you want something truely utilitarian, whether it be to ride across the country, take a boat to the river, or run a truck-free landscaping business, specialty bike trailers exist to do it.