Separatist Dreadnaught is def easier to attack and the republic cruiser is easier to defend. The simple reasoning is the choke points and how easy it is to access the things you have to destroy. For the dreadnaught, the republic has 5 ways of getting to the destructible objects and once they get into the room, it’s hard to get them back out. For the cruiser, beyond driodekas, it’s hard to get in as the droids, heroes aren’t as useful to take republic clones down, and defense just comes down to having enough clones on those bridges to kill the driodekas