A "well performed" fly sparge will be substantially more efficient. Commercial breweries I've spoken to are achieving 92 to 95% efficiency and they're not batch sparging.
FWHopping has been in use for centuries. It's been tested by time and in modern labs where it has been shown that the time the hops spend steeping in the wort during runoff exposes them to a higher pH, increasing utilization which results in higher bitterness levels. Because the hops are steeped before boiling, many of the volatile aromas and flavors you'd typically lose in the boil are "locked" in (this is also true for mash hopping) It also helps keep foaming down as the boil starts, reducing the chance of boiling over. It may be debatable and debated, but the technique has been in use this long for a reason. I can suggest some books if you are interested in learning the undebatable facts about FWH and the chemistry behind it.
Clarity is overrated, but I personally prefer my beer to look as nice as it tastes. That said, a vorlauf is among the many things I do to achieve this (whirlpool, finings, cold crashing) The more solids I can remove at each step of the process, the more effective the next method will be.
For a 5g batch, batch sparging makes sense in regards to time. For anything larger where you wouldn't or couldn't lift/pour that volume of fluid you'd need valves. If you're going to go to that length you might as well fly sparge for many reasons, and you won't be losing time since you can heat the wort during the runoff. As it's been pointed out in previous posts, the wort in the kettle will be boiling before sparging is even complete.
I don't worry about time, however. I don't brew unless I've got an entire day to devote to it. It doesn't make sense to me to quicken and cheapen the process as much as possible. That's what AB has been doing to us for decades. A little extra time, effort, and investment means treating myself and my friends to a truly unique, high quality product and I benefit from the joy of perfecting a craft rather than rushing through it.
Again, comparing commercial breweries is not relevant to the average homebrewer. They fly sparge because they brew such large volumes that batch sparging is not time or effort efficient. This is not the case with most homebrewers.
Again, my point about choosing the sparge method to FIT YOUR EQUIPMENT still stands. Commercial breweries utilize equipment much larger than the average homebrewer. The are pretty much forced to do a fly sparge. They have tuned their processes to utilize as much from the grain as possible because a 5% gain in efficiency is a huge amount of money.
Now if you brew more than, say, 10 gallons, I'd argue you weren't the average homebrewer. More power to you, but the stats force you out of that category.
FWH hasn't been much interest for me, but I'm always ready to read some books on brewing. I'd be curious to see the physics behind FWH explained. I'd also like to see more experiments and tastings related to it. I'd love to sit in on a blind tasting, ala Brulosopher's xBEERiments, but so far the opportunity hasn't arisen.
As far as clarity, perhaps a bit of clarity is in order. What I mean to say is that clarity pre-boil doesn't necessarily equate to clearer beer. I haven't seen any evidence that removing particulates ahead of the boil means clearer beer. From my experience there are other factors, such as yeast selection, temperature, water chemistry, etc. give a higher clarity. Turbidity in preboil wort contains very large particulate. Those are the things that are going to settle very quickly in the fermentor. The wort itself contains proteins, especially when you add hops and other things into the boil. Those proteins are unseen in clear wort, but in the boil are coagulated into larger groups, which settle out as hot break. That, and yeast, are the main contributors to cloudy beer, not the very large particulates that make wort cloudy from the mash. Those larger particles may actually aid the smaller particles in settling to the bottom of the fermentor.
As anecdotal evidence I could point to the many brewers who don't vorlauf at all and who make perfectly clear beer.
I know it seems that clear wort makes clear beer, and as I have said, I still usually do a vorlauf, but test results haven't show it's not nearly as effective as some other things that people could do, and side-by-side tests actually show it's not effective at preventing cloudy beer any better than a good vorlauf. When my recirculating system is finally working, I may fly sparge and end up with perfectly clear wort going into the BK, but I don't expect it to translate into clearer beer.
Your value of time may differ from mine. I am not likely to have a full day to spend brewing, nor do I care to spend a full day brewing. If I can do things that make my brewing fit within my allotted time, I'm glad to not have the stress of brewday extending into whatever else may be going on. I spent years obsessing about homebrewing; reading about it, building things, brewing, doing all aspects of it. But I don't aspire to be a professional brewer. In the end I realized it's a hobby. That makes me beer. It's not worth it for me to focus so much time and energy away from home and family and friends.
So if I can mash for 30 minutes instead of an hour and not notice a difference, I may do that. If I can clean during the mash and boil, I do that. Sometimes I do a no chill (although in my experience I'd rather not) so I can attend a family thing, I do that. Since I've gone to an electric system heating the wort in the BK at first runnings isn't always an option. I have to cover the element and then some, before I can safely start heating. The convenience of electric brewing is worth the very small additional time it takes to heat my wort to boiling. It will be even better when I have a timer built into my system so I can have strike water already hot when I want to brew after work.
Those things that I choose to do to save time are generally the least likely to cause a difference in the final beer. And I still experiment with things to get the best beer possible. I don't delude myself by pretending that I am operating a commercial brewery. There is a difference between brewing at the homebrew scale and operating a financially viable brewery with investors to please.
You can call me lazy and I won't argue. You could say my standard are not up to your standards, and you'd likely be correct. Everyone has their own expectations from this hobby. Bottom line, is that I don't believe Fly Sparging makes a better beer than Batch Sparging. You make points that you feel make it better for you, but some of those are debatable, and many aren't necessarily advantages for others.