I've been keeping up with this thread but haven't had much to contribute until now. I had a bit of a "breakthrough" with the ASG-1 yesterday. I had been pretty satisfied with the sound and fit while using a dual flange tip, but I figured it couldn't hurt to try some others. After a few mediocre results, I ended up finding my perfect match.
Unfortunately I don't know where these tips came from. I keep all spare tips in a collection together and I can't recall when these were added. They look like the medium Sony hybrids with the green inner section, but I know they aren't from a real Sony product. Anyways, these were the missing link I needed to get great sound and great comfort from the ASG-1.
I was listening to Illinoise by Sufjan Stevens (a perfect example of music sounding great despite using very low budget recording equipment) and the ASG-1 sounded up there with some of the better customs I've encountered. This album is full of unique sounds, from wind chimes to wine glasses used as instruments, and some interestingly complex arrangements. The ASG-1 gave it a "live" feeling, had plenty of low end extension, and did the voice just right. The only thing that I didn't care for was a bit of a "ringing" type feel on some of the upper mids, though it wasn't too objectionable. I'm hearing them generally the same as ericp10 is.
I've decided to close up the adjustments on my AS-1b and focus on the similarities/differences between the custom and the universal. I think that is more relevant to the discussion at the moment, rather than trying to "figure out" all the variations of the AS-1b. So far I believe they are pretty close in general sound quality. The main difference I'm hearing is the low frequency reproduction - through bone conduction or possibly just a superior seal, the AS-1b seems more effortless and lifelike when reproducing lows. Not that the volume is much different, but the quality is just better. I also hear a bit more in terms of layering and instrument separation. Basically it is the same sound, just further refined. Without taking the venting and bass adjustment options into consideration, I would say the extra $100 jump in price from ASG-1 to AS-1 is worth it. Especially considering the free impression kit which allows you to avoid audiologist fees. That said, I'm very glad Aurisonics offers the universal version , as there are plenty of benefits to going that route.
Those tips sound a lot like the Radio Shack Auvio silicone tips. They are almost identical to the Sony.