My wife and I use Britax and Diono. We started with Diono, but upgraded the older boy to Britax once the wife got her new Explorer, because Diono wasn't seatbelt airbag certified (at the time, they are now).
The Britax are easier to work with, because you can adjust the strap height without having to remove the entire car seat. And our older son (almost six years old) is able to buckle himself with the Britax, whereas we had to put him in with the Dionos. We will be upgrading the younger one to Britax in the next year.
Both are perfectly safe for inflatable belts though.
**EDIT: It's also worth noting my wife researched the absolute f*ck out of car seats, so it certainly wasn't a fleeting decision. **