You can freely connect FireStudios in chain or in parallel (each connected to own port). There are no differences.
The only time there may be a problem is if you are also connecting "other" firewire devices like an external HD.
It might cause issues with the FireStudios in parallel. Most times, you need to chain "other" firewire devices.
However, it may work just fine. Depends on the devices, the firewire card and the computer.
I often have had 2 firewire cards installed. Connect my FireStudios to one card and "other" firewire devices to the 2nd firewire card. This usually allows everything to play together nicely.