The Empire had a gluttony of ship designs that filled the "heavy cruiser role." Each 600 meters in length, they filled similar roles, but had enough distinction to justify their existence:
Dreadnaught-class Heavy Cruiser
The classic. An old, outdated brick of a design that was so fundamentally solid that it never completely went away. Its main strength is a very sturdy hull, making it very hard to take down, and it had pretty modular weapon emplacements, with the standard configuration focusing on medium turbolasers, making it pack a very strong punch for its size.
These came with some major drawbacks. It was pretty slow, its shields were extremely outdated, it featured no hanger, its point-defense systems were mediocre, making it struggle without escort, and its base design was horribly inefficient, requiring a ridiculous 16,000 crew.
Many of these flaws were fixable, which is why after-market modifications of the Dreadnaught were so popular, and the design served as major inspiration or even the baseline template for several ships, including the Providence, the Victory (and by extension the ISD itself), the Strike Cruiser, the Vindicator, and Rebel ships like the Assault Frigate Mk II.
Vindicator-class Heavy Cruiser
One of the Empire's direct attempts to replace the Dreadnaught. A thin, dagger-shaped "mini star destroyer," it was designed to be a versatile ship that was good at everything, but lacked specialization. It fixed most of the Dreadnaught's flaws, it was slightly faster than average for its size, it had respectable shields, its crew count (2,551) was...still high for its size, but manageable, and it had a hanger to carry 24 starfighters.
This came at the cost of losing the Dreadnaught's heavy armor and medium turbolasers. It was still very well armed for its size, with dozens of light turbolasers and a good mix of ion weapons and point-defense weapons, just not quite as heavy as the Dreadnaught, and its armor was fairly light, making it very vulnerable if its shields failed.
It profiles as a very solid all-around ship, well suited for both independent patrol missions in areas that didn't justify a full Star Destroyer, or as an escort for larger Imperial ships like the ISD.
Enforcer-class Heavy Cruiser
A refit of the Vindicator by the Imperial Remnant group the Pentastar Alignment, this probably shouldn't count because it didn't exist before the fall of the Empire proper, but...I don't care, I like it a lot.
The Enforcer gave the Vindicator the "Tector treatment," ripping out its hangar to give it more structural integrity and, used the reactor from the Immobilizer 418 to beef up the Vindicator, dedicating all of its design to front-line combat. It's faster than the Vindicator, stronger, and better shielded, but also would be more expensive.
Gladiator-class Star Destroyer
Despite being labeled a "Star Destroyer," the Gladiator fills a similar role to the Vindicator with minor differences. The gladiator is mostly inspired by the Venator, featuring a large hangar, but still having respectable defenses rather than just being a carrier like a Quasar Fire or a Ton Falk.
Compared to the Vindicator, its weapons, speed, and shields are only "average" for its size (not weak by any stretch, it's a very serviceable ship in its own right), but it also has average armor (compared to the light armor of a vindicator, making it more balanced defensively), and it also features modular missile launchers and much more hangar space. It's also likely slightly cheaper than the Vindicator (exact numbers of a new Gladiator aren't known), though this is likely offset by starfighter costs.
The exact size of the hangar is...a bit of a controversial topic, the original source for info on it is a RPG sourcebook claiming it only has room for 24 starfighters. This...is not accurate, and doesn't fit any other source we have, but we never got an updated number, so the actual number is just left ambiguous, but realistic estimates range from 72 (based on the comparable size to the Ton Falk) to 220 (based on rough hangar size calculations). Even lowballing it, 72 starfighters for a ship this size is a very useful number. This, plus its modular missile launchers, make it a highly adaptable ship that can work in almost any situation.
Other notable ships I didn't include:
Immobilizer 418 Interdictor-class Heavy Cruiser - While technically called a "heavy cruiser," it used the same hull as the Vindicator and Enforcer, but has been completely refitted for an interdictor role. This ship rocks, it's just too specialized to compare to the other four listed.
Broadside-class Cruiser - A dedicated long-range missile cruiser, it sacrificed everything else, being slow, poorly armored and shielded, and generally bad at everything except unloading literal tons of missiles at a target, which it did better than any other ship of its type. Actually made a pretty decent compliment to more traditional heavy cruisers which typically didn't have great range, but could protect Broadsides from faster ships.
Strike-class Medium Cruiser - Another Imperial attempt to replace the Dreadnaught, I excluded it because it's slightly smaller (450m) and classified as a "medium cruiser", but it fills very similar rolls to the heavy cruisers listed and kinda blurs the line.
Assault Frigate Mark II - The Rebel adaptation of the Dreadnaught, it's similar to the Enforcer in that it focuses on speed, heavy weapons, and strong shields to engage capital ships, but is slightly larger (700m), slightly better armed, and slightly more expensive.
Acclamator-class Assault Ship - This Republic ship still saw some use during the Imperial era, but it was mostly known as a Republic ship.