As for the straight A frame. It's a pain to hook up and store. The colapsable, self locking arms on the others make hook ups an easy one man job. As for steel vs aluminum, each has it's place. Mine stays on the back of the motorhome, I simply fold the arms and place a cover over it, so I opted for the stronger (heavier) steel. If, for whatever reason I wanted or needed to remove it frequently, I'd go for the aluminum, if my toad was well under it's rated capacity.
Jay & Peggy Monroe with Dolly
Can't take it with you - don't plan on leaving any behind
2016 Newmar London Aire 4553, Spartan chassis
Wrangler Unlimited toad