We recently switched from Scott Air packs to the MSA FireHawk M7. When we had the Scott Air Packs, we were using the Scott brand communication set. Similar to the Hazmat radiocom, but it was a little older. What I really liked about the Scott system was how the speaker was held near your ear. It was simple to attach to the face piece and easy to use. Make sure that you get the connector that fits your brand and model of radio.
Now that we have switched to MSA, we are using the MSA Clear Command system. http://www.msanorthamerica.com/catalog/product852.html
One problem is that they don't make a connector for our current brand of radio, the Vertex. So we are using our older radios, the Motorola HT1000. I think I like the Scotts better, but we are using MSA now, so I guess we have to get used to it.