The first model was the favorite weapon of the Mariposa super mutants during the Unity's time, and allowed most or all of the super mutants to wield them effectively with only one arm.
The CZ53 is an excellent big gun, especially since it is one of only 3 big guns in Fallout, and one of the more common big guns in Fallout 2. It does well at mid- to close-range shooting, where its 40-round bursts can tear apart small groups of enemies. At longer ranges, fewer bullets hit, resulting in lower damage due to the small bullets it shoots. The hollow-point round multipliers create ridiculous amounts of damage, while AP ammo is mostly useless due to engine glitches and miscalculations.
All in all, it is a fine weapon for Fallout, while the Avenger minigun one-ups it for Fallout 2. Paired with a Rockwell BigBazooka for long range, it lets big-gun characters overpower almost any opposition.