This is the only post on this thread I am competent to reply to with real-world data so I am very excited about that.
I have a nice portion of my library recorded in Itunes Plus (which is Apple AAC 256 VBR). For my ear it is transparent, full stop. The chance that I am guessing on ABX testing is 100 percent (sorry about that Bigshot, I am also practicing listening for the gurgling aquariums at 96 kbps in Frau CBR on the Sammy Davis, Jr., CD, now, I promise, although my CODEC has not yet seized up. I do look forward to that though.). As to whether Apple AAC 256 VBR caps out at 256 kpbs, the answer is no, and in my library, the
average bitrate is considerably higher than 256 kbps for most songs ripped in Apple AAC 256 VBR. The
lowest is 233 kbps for only two songs (a song from the Duke Ellington Blanton-Webster band, and a Pokemon song (it's one of my kid's, but I rip everything in the family and we share an Apple Music account). The Apple AAC 256 VBR rips max out at an
average bitrate of 304 kbps (of course some passages in the file will be higher), interestingly for a few 1950s and 1960s jazz recordings (Oscar Peterson, Grant Green, Eddie Harris); and at 303 kbps I have a lot of modern jazz recordings. The Apple AAC 256k VBR encoder doesn't seem to up the bitrate that high even for the better classical recordings. The highest classical track is a Dvorak Slovic dance at 290 kbps. The range from 233 kbps to 304 kbps is a pretty smooth progression literally including muliptle instances of every single bitrate in-between. The median is definitely 256 kbps on the button--I don't even need to count--there are a ton of tracks at that bitrate. The mean average is higher. Just looking at the distribution I'd ballpark it at 275 kbps.
For me Itunes Plus is transparent and set it and forget it, but I do agree with Bigshot that some of the space it is taking up with these higher bitrates is a waste of resources. It's just super-easy.
Now you and this thread have me paranoid about my signal chain in terms of bluetooth streaming.
How the heck am I going to ABX that for peace of mind? I always just thought to myself, that sounds pretty good! Ignorance can be bilss, I guess. Until some huckster rips you off. I moved over from OS X to Windows 10 recently because I like Windows 10 better than OS X (gasp!) (we have both in the house, between me, my wife and three kids), and Apple is doing some increasingly weird stuff with its 27" Imac line, making very it hard to DYI upgrade for most things, and with 20/20 hindsight the Imac bluetooth was a lot less stable.
I believe I have an intel wireless / bluetooth device in the Windows computer I am using now. Wait, let me check speccy--yes, it's an Intel dual band AAC Wireless AC 3165 and bluetooth transmitter and receiver. I can always get the state-of-the-art driver for it and automatically install it using the Intel site. So that much of the chain I feel pretty good about. My setup also much more reliably remembers and automatically connects to my previously connected bluetooth devices than my Imac did. . . sometimes better than I want it to. I decided I had had enough of the folks at Apple and gave my 27" Imac to my mom. I would use a non-Apple codec if Apple AAC wasn't a no-brainer. Windows 10 and third-party monitors have finally gotten to the point where I trust them for photography, and I was personally able to get more performance for less money than Apple would charge and more focused on my needs than Apple would allow me. Now I am shooting 99th percentile on Passmark, with a focus on my preferences and needs, for way less than I could get that through Apple, by thousands of dollars. Photoshop and Lightroom scream. Gaming performance is beyond great. Sound stuff is a piece of cake. Our portable environments include lots of both IOS and Android devices. Plus we have both Apple TV and Roku. So I have every single variable mentioned in this thread at play. Everything has to work smoothly and well because we usually have something in the area of 30 devices connected to the network at any one time (3 teenagers!) and I don't pay the cable man for my TV media anymore.
The info on the interweb is both plentiful and vague on the comparative bitrates of APTX, AAC and SBC but as I understand AAC is capped at around 256 kbps and APTX around 350 kbps?
I regularly switch between iOS and Android I am curious as to the real world limitations of wireless headphones on an iPhone vs APTX equipped droids? e.g. using Apple Music and it's 256 kbps AAC should mean no loss but I'm unsure how higher bitrate stuff like Spotify 328 kbps or the standard Tidal 328 kbps AACs would compare and how much of a bottleneck the AAC codec would be on an iPhone?
With aptx-hd now available on both phones and headphones I am wondering how much of a real world quality advantage Androids now have with wireless headphones?