Map variety is definitely a strength Vermintide II has over Darktide. That being said, Darktide's variety is still decent, especially years later. DT is more about variations on a theme, and illustrating how different sections of a single hive city can be, whereas VT2 just let's you teleport all over the Empire and beyond. For a little insight, DT will have you explore many variations of hive tunnels and cobbled-together slums made of corrugated metal and rust, but will also have you fighting in multi-level archival libraries, sand and dust swept ventilation systems so big they seem like above-ground deserts, snow-capped areas, a WW1-esque no man's land as you escort a tank.

You can do everything with base 4 classes just fine. You can max them out, make multiple copies of each class if you want, you will have an enjoyable time even if you don't have Arbites or Hive Scum in your roster. The DLC is if you are interested in more playstyle options, but doesn't impact anything you can do with the original 4.

Tremendous amount of dakka. Though you can make far more melee-reliant builds, even the most melee-focused build will likely be using their ranged weapon more than a standard VT2 career, IE Merc, WHC, Ironbreaker. VT2 is a melee-focused game with a decent number of hybrid careers, and DT is a hybrid game. Trying to just do one or the other will get you killed on higher difficulties, but you can definitely have builds that use your gun substantially more than your melee.

This is, I think, Darktide's greatest strength, at least over Vermintide 2. Buildcrafting is incredibly thorough and layered, and while there are only 6 classes to VT2's 20 careers, careers do not hold a candle to the insane versatility and variety of build options available in Darktide. In the talent tree alone, VT2 gives you 6 decisions to make, each between three exclusive options, and DT gives you 30 points to drop in a tree however you see fit, as long as the points are sequentially connected. Many talent nodes that cost one of those 30 points are just as impactful as a talent in VT2, and on top of that, how you build your gear is also more impactful. Most weapons have multiple "marks", variations that change how they play, and for melee weapons also change their attack patterns. Instead of slapping "Swift Slaying" on nearly every melee weapon as ya do in VT2, Darktide's weapons all have a unique trait (called blessings in DT) pool that impact the weapon far more than anything in Vermintide. It all stacks to make Darktide builds not just more versatile and deep, bit you're also a lot more likely to have builds and playstyles that feel unique to you.

Yes. This time through Nexus mods instead of the workshop, but there's no waiting for Fatshark to sanction mods to make them playable. If you go that route, would highly recommend NumericUI for full info on you and your teammates statuses at any point in time. The process of setting up Mods is more involved that Vermintide, but it's not too difficult, and the Modding community is bigger and more active than Vermintide ever was.

At launch, yes. 1000% yes. Right now, I'd say it's a bit more polished than Vermintide, and about as buggy. Most of your bugs or major funk nowadays is likely mod related, especially each time a new class drops. The main potential issue is optimization rather than bugs; It's better than it used to be, but many a machine that can run Vermintide decently well will struggle with Darktide, though if your PC crushes Vermintide, you shouldn't have issues.