Actual time for hitching up and unhitching with a dolly vs 4 down may be fairly close, depending on various factors. The big difference between the two is this:
1. With the dolly, you're going to be crawling around on the ground more when hitching up and unhitching (to attach chains underneath car, for example). With a 4 down setup, the things you attach, unhook are higher up, eliminating the need to crawl on the ground like you sometimes have to do with a dolly. That bothers some folks, but not others.
2. With the dolly, the things you have to do (put on or remove straps, hitch dolly to MH, etc) typically will involve working with things that have the potential to get you much more 'dirty', especially if its wet out or raining. Hitching up and unhitching a 4 down setup is typically not quite as 'dirty'. Therea again, some folks will be bothered by that, some will not.
3. Get stuck just ONCE in a spot where you have to back up and have to unhitch, re-position, then hitch back up, and you will see where the huge difference is. 'Tis much more complicated and more of a 'PITA' to do that with a dolly setup than 4 down.
Like already said, its a personal preference thing, each approach has its pros and cons. As I alluded to here, though, there's a lot more to consider than just the actual time it takes to hitch up or unhitch.
Will and Cheryl
2021 Newmar Baystar 3014 on F53 (7.3 V8) Chassis ("Brook")
2018 Jeep Wrangler JK ("Wilbur")