I fly sparge.
I have the advantage of first wort hopping, excellent efficiency, clearer run-off, and a period of time with free hands to do other things. I also brew 15g batches and batch sparging wouldn't save me much time or effort by comparison, and I'd sacrifice all the above advantages.
Efficiency difference is generally negligible, from what I've read. Meaning that a well-performed Fly Sparge may be slightly more efficient than a well-performed Batch sparge, but the difference is pretty small. not enough to make me choose one over the other.
As far as FWH goes, I cannot say as I have never tried it and never personally performed a side-by-side comparison on the same beers brewed with and without, let alone a whole battery of different beers brewed both ways. From what I've read, the whole issue of FWH is debatable, and debated. I can't understand how it would make any difference by the time the beer is finished, but that could be that I'm not knowledgeable enough in the chemistry of the entire brewing process.
Clear run-off isn't necessarily an advantage. I've read a Brulospher ExBEERiment that seemed to indicate that running clear wort into the BK did not improve the final beer. And I've heard a lot of anecdotal reports that indicate boiling all that stuff works as good as a good vorlauf. I know I have a hard time not doing a vorlauf because it seems so wrong to think that clear wort doesn't help make clear beer, but the few batches I've skipped it, and used a healthy does of calcium in the mash and kettle, have come out VERY clear. They seemed to look and taste as clean as any other beer I've brewed.
I'm not sure a fly sparge would save me time. Generally, by the time I'm sparging, I have been sitting there waiting for the mash to complete and have nothing important to do but get the boil going. If I can quickly run the mash tun dry, I can start the heat. Then the faster I can rise those sugars and empty the tun again, the sooner I can clean the mash tun while the boil heats up.
If my equipment were different, then fly sparging might be an obvious advantage, but I don't see it with my current setup.
This really is one of those areas where it's strictly a matter of personal choice.