I think you answered your own question, almost. You can flop your cab by driving under low trees or through a low overhead clearance doorway. The problem is unflopping it.
My solution was to make my tractor-building entry points taller than the cab. As far as the trees go, ROPS or cab, I prefer to trim all the lower branches off to a height of about 10 ft or a little more, depending. I may allow a "NICE" branch at 8 ft. Low branches get in the way of haying, brush hogging, parking in the shade and reduce the view, shade and kill grass, and look unkempt (personal pref.)
Cab style ROPS vs Rollbar style ROPS is not ever going to be a valid which is better choice without qualification. Either is the BEST solution for some things. Both have tradeoffs, their plusses and minuses, and neither is the BEST for all tasks and personal preferences. Not everyone buys a convertible. That doesn't mean they don't have a place. Sedan vs coupe, which is better 2 doors, 4 doors, hatchback or trunk. They all have good and bad points. (Oh, a chicken coup has only 2 doors, otherwise it would be a sedan!)
If my tractor was essentially a lawn mower and I didn't make much dust, spray dangerous chemicals, or work in inclement weather, I'd see little justification for a cab. Some tasks can be postponed (called on account of rain, snow, or whatever) but if you have a heard of Angus or some brood mares or whatever depending on you then you have to go out in all sorts of weather to meet your obligations.
I have friends and neighbors who usually discharge their responsibilities to their stock with great dependability in all sorts of weather without cab tractors (with associated personal sacrifice such as getting wet, cold etc.) but that isn't my first choice. Some folks claim getting in and out of a cab a lot is a hassle of much grater magnitude than the effort without a cab. Could be in some cabs but not mine. I get in and out with great ease, no harder than the open rigs I've run.
What is the answer to the question: "What is the best tool?"
It depends. Don't we need to know a few things? What tools is the user proficient with, what tools are available, what tools can be afforded, what tools are a fair fit to the job, and on and on.
To a man who only has a hammer, every job looks like a nail!
So far as ever settling the "which is best, cab or open" question, the only good answer is, "It depends."
Versatility matters. I can drive a screw with a hammer but it is tough to drive a nail with a screw driver.
I can do most tasks with a cab on a tractor, although backhoe requires a bit more fuss. I can't drive my tractor through a low overhead door built for cars, or for that matter through a 3-0 front door, down the hall and into a spare bedroom either.
Everyone has to make their own choice based on usage, their budget, and personal prefs. If cars only came in one color per brand would you pick your car by color pref or other features irrespective of the color of that brand?
If you bought only convertibles you could save money on garage doors and drive under trees easier. If you really don't mind being out in the elements you don't need to put the top up or use the heater. Of course the hatchback might be a hassle when mounting a backhoe but it might be easier with a trunk.
