That's not a worry anymore with name brand aluminum trailers. Every weld on mine is really good and even the decking is fully welded to the frame members. My dealer sells hundreds of them a year and hasn't had any problems. Just be sure to get the Dexter axles on any trailer you buy now and tires rated higher then your actual towing speed. Chinese tires and axles are the biggest problem these days on all trailers. I also have a 16 ft steel 7k trailer but don't want to haul around the extra 1,200 pounds now that I downsized from a F350 to a Ranger with only a 7500 pound tow rating.Be careful with an aluminum trailer ! Not every T,D &H can WELD aluminum !!! Might not be huge deal if close to home but on the Interstate could be an issue.
FYI basic ,entry level 'car hauler' is $6K out the door here in Hamilton,Ontario.