According to the tiers of warships, frigates were the lowest, followed by destroyers, next were battlecruisers, then battleships, and, finally, the largest, the capital ships.
Battlecruisers possessed incredible firepower and top-of-the-line, long-distance traveling capabilities. If someone planned to travel from Endaro Star Region to Black Abyss, which was tens of millions of lightyears away, cruisers were obviously better than frigates.
For example, if there was an unexpected meteor shower in the middle of the journey, the cruiser would be able to utilize its large energy shield and proceed as usual, but the same situation would be a disaster for the smaller frigate.
The advantages of the frigate were its mobility and difficulty of detection, whereas battlecruisers did not have such bells or whistles. There was only one course of action when it encountered an enemy: blast them with its huge firepower.