I think it's widely accepted that the 3G Tour Ultras are more comfortable than SSTs, but good God are they one of the ugliest shoes I've ever seen. I had the old style SST8 they were still in perfect condition after 8+seasons, I just wanted to upgrade to the 9s for looks. The 9s are significantly less "blocky", much lighter, but still far from a tennis shoe if we're being completely honest.
I have the BOA system, and am a huge fan. It's so quick an easy. I'm probably a bit biased due to previously being a snowboarder, which is where Boa made it's name in the industry. Which should really help quell any concerns about durability. The C9 Knits look like they could potentially be more comfortable, but I have no complaints about the SST9, and I don't cover enough distance in my bowling shoes for concerns to really pop up.
If I had to run a mile in my bowling shoes, then I'd probably have some major concerns or complaints, but the 10 steps from my seat to the approach, is not enough for me to ever even notice the shoes on my feet.
The 8s use to come with a whole sole\slide combination pack which was awesome. The 9s come with only 1 slide and 1 heel, which was disappointing given the price we pay.
Don't let the Boa system dissuade you. If you prefer the comfort of the 3Gs, completely understandable, but lace system should not be the deciding factor, in my opinion. Best of luck.