Indeed, Michael - they're both lossy, but broadly speaking the AAC compatibilty is the iOS equivalent, quality-wise, to aptx on Android.
I guess you could argue that and I do not believe AptX has any advantages over AAC really. It is probably more about CPU and energy consumption. I notice when I play bluetooth music on my computer (and my phone) that it drains the battery quicker. When I use my MacBook Pro I can see a process that is coding the music to be sent to the headphones take up quite a lot of cpu. Also it would not make much sense to re-encode music - but I believe this is happening on iOS as well.
One could argue that since the music we listen to mostly is lossy, and probably in AAC or any similar codec - AptX wouldn't make any difference at all. It is just an alternative to what bluetooth used to be for music back in the days.
Anyways, enjoy your music people. I sure do!