I consider the Kar Kaddy SS to be the best but there are many good ones, each with advantages. It is well construcked and will haul a large vehicle, but is also higher priced than most. Things to consider:
What are you planning to tow - weight, width, clearance, etc.
Where will you store it - the SS folds, others can tip on end.
Price - they range widely in price. I think you get what you pay for. Not everyone needs the most expensive one. We bought a used one.
Steering - I would go with a rotating tray at a minimum but there is a risk on some that the dolly tire can contact your vehicle on a tight turn. On the SS, the wheels turn and it tracks well. . I don't think any of them handle real tight turns very well.
Just my thoughts. Hope this helps.