It depends on your network, and there's not enough information there for anyone to be able to tell you for sure. You can assign as many subnets and IPs to a routed interface as you want however. The only reason to use a bridge is if you wanted those subnets across multiple layer2 interfaces.
well I have a bridge setup with ports 3-12 on the CCR, port 1 is my connection back to the world and port 2 is my connection to the next hop down the line. Now the 10.x.x.x are the IP's we give our customer subscriber units, the Public IPs are obviously what they're routers pull DHCP from this router. Now I had created the bridge but had assigned the 10.x.x.x/24 to port 3, 198.x.x.x /24 to port 4 and 198.x.x.x /24 to port 5. But looking at it, it just didn't seem right to me considering on my 7507 I had all those IP's on the Local Fast Ethernet Interface. I guess that's the only reason why I'm second guessing myself, plus I'm working on limited sleep as well.