Having towed by all 3 methods I choose 4-down.. Recently I had some work done on the car. I towed it in (Since the shop was like 20 yards off my "Beaten path" and the job was way easier to do with a cold engine) and when one the mechanic drove it up to my rig where I hooked it up.. When he gets around to the RV life he decided right there he'd goong 4 down too.. I was fully hooked faster than he could get the webbing over one tire.
That said.. What I would look for on a dolly is a good "Stop" (Parking stop) the part you "Bump up" against when you pull on.
Was in a campgrond last winter and heard a loud "WHOMP" the party was putting the car on the dolly on the road in front my pull through site The dolly only had about a 1 or 1 1/2" stop and the car went right over it and WHOMP.. We used jacks and planks and still had to call a tow truck to pull it back onto the dolly (Minimum tow bill. thanks to my planks and jacks) That would have been a much harder job with just the tow truck.
SO look for a good STOP for when you pull on.